SEO and SEM,
with judgement.
Organic positioning that builds long-term asset + Google Ads campaigns that pay back in performance, designed together as a system. Most organisations pay twice for traffic they could capture for free — and the other way around. The judgement lies in integration.
If you are deciding where to invest so that your business shows up on Google, you have probably run into two acronyms that get mixed up all the time: SEO and SEM. They look alike, they play on the same stage —search results— and yet they follow very different logics. This guide explains what each one is, how they really differ and, above all, how to decide which one is right for you depending on the stage your business is in.
SEO (Search Engine Optimization) is the set of techniques that get a page to appear in Google's unpaid results. You don't pay for each visit: you work so that your site «deserves» to rank high in the eyes of the search engine.
SEO is not a single thing, but three fronts that hold each other up:
On top of this comes local SEO, decisive if you sell services in a specific area: a well-kept Google Business Profile, managed reviews and geolocated content can be worth more than a thousand generic links.
The defining feature of SEO is time: it takes a while to get going —counted in months, not days— but what you build stays. Good content keeps attracting visits long after you publish it, without paying for each click.
SEM (Search Engine Marketing) is the capture of traffic from search engines through paid ads. In practice, when people talk about SEM today they are mainly talking about Google Ads (and, to a lesser extent, Microsoft Ads for Bing). You bid to appear when someone searches for certain keywords, and you normally pay for each click you receive.
SEM covers several formats depending on what you sell:
The advantage of SEM is immediacy: you switch on a campaign today and you can get visits today. Its limit is just as clear: the traffic lasts as long as the budget does. The day you turn off the tap, you stop appearing.
Beyond «one is free and the other is paid» —which isn't exact either, because SEO also costs time and work— these are the differences that change a decision:
| Aspect | SEO | SEM |
|---|---|---|
| How you pay | Investment in work and content | Pay per click / impression |
| Time until you see results | Months | Immediate |
| What happens if you stop investing | The asset remains and keeps working | The traffic is cut off abruptly |
| Type of return | Cumulative over the long term | Direct and measurable instantly |
| Control over position | Indirect (Google decides) | High (raise the bid and you appear) |
Put another way: SEM is like renting visibility and SEO is like building an asset of your own. Neither is «better» in the abstract; it depends on what you need and when you need it.
SEM shines when you need results now: a launch, a seasonal campaign, validating whether a value proposition converts before investing months in SEO, or defending your brand when a competitor bids on your name. It is also the natural route in sectors where SEO is painfully slow to conquer and you need a presence in the meantime.
SEO is the smart bet when you are thinking medium and long term and want to reduce your dependence on advertising. If every year your cost per click rises and your profitability falls, that is the signal that you are propping up with money something you could capture with content and authority. SEO done well means that, over time, you depend less on the Ads budget.
The question «SEO or SEM?» is usually badly framed. In most companies the answer is both, but coordinated. SEM gives you immediate traction and real data on which keywords convert; that data feeds your SEO strategy. In turn, as SEO gains positions, you can lower the bid on those keywords and reinvest the budget in growing, not in holding on. Treated as a system, they stop competing with each other and start to multiply.
The most common mistake I see is managing SEO and SEM in watertight compartments: one team (or one agency) handles the ads, another the content, and nobody looks at the whole. The result is companies that pay twice for traffic they already had, or that cannibalise their own organic results with unnecessary ads.
Integrating them well means starting from a single keyword map —ordered by business value, not just by volume— and deciding, for each one, which channel works it best: the high-intent, fast-converting ones go to SEM; the informational, long-tail ones go to SEO. And, on top of that, an attribution model that reconciles both channels so you know what each euro contributes. If you want to go deeper into that part, I develop it in attribution models.
It is worth not confusing this with brand positioning, which is a different strategic task: the place your brand occupies in the customer's mind, not on Google's results page.
And a layer that is increasingly relevant: search no longer happens only on Google. With the arrival of AI Overviews and assistants like ChatGPT or Perplexity, a new discipline appears, optimisation for generative engines, which I explain in GEO: how to rank in ChatGPT, Claude and Perplexity. It does not replace SEO: it extends it.
Neither in the abstract: it depends on your horizon. If you need immediate results, SEM. If you are looking for an asset that pays back over the long term, SEO. In most companies the optimal approach is to combine both and treat them as a system, not as rivals.
SEO achieves visibility in the organic (unpaid) results by working on content, technique and authority; it takes months but it stays. SEM achieves visibility through paid ads; it is immediate but it stops when you halt the investment.
The first indicators usually arrive between months 3 and 6, and sustained traction from month 9-12 onwards. Anyone promising SEO rankings in 30 days is selling smoke or using risky techniques that Google ends up penalising.
There is no single figure: the cost per click depends on the sector, the competition and the quality of your ads and landing pages. The good news is that this cost can be brought down quite a bit by aligning the keywords with the real intent and improving the page experience, which raises your quality score.
SEM is the capture of traffic from search engines through paid advertising, mainly Google Ads. It is used to appear immediately in front of anyone searching for what you offer, ideal for launches, seasonal campaigns or for validating a proposition before investing in SEO.
Yes, increasingly so. The foundation of SEO —well-structured content, clear entities, structured data and authority— is exactly what generative searches use to cite sources. It is an additional layer on top of classic SEO, not a substitute.
If 70% of paid traffic is from Google and SEO is forgotten, you're paying eternal rent for something you could build as your own asset.
You rank well for irrelevant keywords and poorly for those that really convert. SEO without strategy is decorative noise.
You generate many leads in SEM but conversion to customer is poor. Usually a keyword-intent match problem, not a creative one.
Service business with geographic presence. If Google Business Profile and local SEO aren't well tuned, local visibility dissipates.
I review GSC, GA4, Ads Manager, web structure, content and competition. I detect tracking gaps, lost keywords and overlaps between organic and paid.
I build the keyword map prioritised by business value, not just volume. Each keyword with its intent (informational, commercial, transactional) and optimal channel (SEO or SEM).
On-page and technical optimisation, pillar content, link-building with judgement. In parallel, restructuring of SEM campaigns with Shopping, Search, Performance Max according to mix.
Attribution model that joins organic and paid in a single dashboard. Monthly iteration with real data, not with hunches.
Treated as a system, SEO and SEM stop competing with each other and start multiplying. Typical results:
When SEO starts to pull, the blended CPC (organic + paid) falls. The SEM budget is freed for growth, not maintenance.
Branded search managed properly: small but defensive campaign, consolidated SEO for your own keywords. Competitors stop stealing your traffic.
Landings aligned with intent + relevant keywords + healthy CTR → quality score rises → CPC drops between 15 and 35%. Without touching budget, performance improves.
A well-built pillar article keeps drawing traffic 3 years later. SEO investment amortises over time — SEM expires when you turn off the tap.
Dashboard with value by channel and by keyword. Mix decisions stop being political and become analytical.
Google Business Profile optimised, reviews managed, local schema, geolocated content. Real visibility for customers in your area.
Online store with total Ads dependency. SEO plan with 60 pillar articles and category restructuring. Blended CAC -28% in 8 months.
El marketing del cerebro es más predictible que el marketing de la opinión. — Ángel Ortega Castro
Professional services firm without organic presence. GBP optimisation + 24 articles linked to real cases. Qualified organic leads +180% in 6 months.
Resort with SEM in 4 markets. Campaign restructuring + attribution model that reconciles direct booking and OTA. Cost per booking -22%.
This delivers particular value in these four scenarios. These are the most typical in mid-sized companies with active but uncoordinated digital marketing:
Cost per click rises without the business growing at the same pace. Without underlying SEO work, CPC will keep rising and profitability falling.
Categorical searches in your sector are dominated by competitors with SEO content, known brand and sustained investment. The gap widens each year.
Visits arrive but conversion rate is poor. Usually a keyword-intent mismatch: you attract the curious instead of buyers.
If you sell local services and your Google Business Profile isn't managed, you're handing revenue to competitors with lower quality but better local SEO.
Neither — it's integration. SEM gives immediate results but evaporates when you close the tap. SEO takes months but compounds. Organisations that treat both as system are those that win in the long run.
First indicators between 3 and 6 months, sustained traction from month 9-12. Anyone who promises SEO in 30 days is either selling smoke or using grey techniques Google penalises sooner or later.
Yes, but adjusting expectations. In highly competitive sectors (banking, insurance, mass-market e-commerce) the top positions are taken by giants with multi-million investment. Strategy focuses on valuable long-tail, vertical niches, asymmetric brands. We don't go after the impossible generic keyword.
Yes. Technical SEO (core web vitals, indexing, structure, schema markup) is part of the work. If your site has serious technical issues, we identify them in the audit and propose an improvement plan — with your technical team or with specialist collaborators.
Yes. With the arrival of Google AI Overviews, Bing Copilot and Perplexity, search is changing. SEO work includes optimising for citation in generative answers: structured content, clear entities, schema and authority. It's an additional layer on top of classic SEO, not a replacement.
First 45-minute session, free of charge and no commitment. If we fit, I send you a detailed proposal within 5 days. If we don't, you take away a useful initial diagnosis.