What is PMax cannibalization?
Malthe Weibeck Thomsen · Growth Hacker · Senior Pull Specialist · 8 July 2026 · 3 min.
Definition
PMax cannibalization is when Performance Max spends budget on, and credits itself for, conversions that would have happened regardless — typically brand searches and bestsellers — so its reported performance is artificially inflated.
Also called: PMax cannibalization, Performance Max cannibalization, PMax self-attribution
Sådan virker det
Performance Max kaster gerne budget efter brand-søgninger og bestsellere, I alligevel havde fået — og tager så æren i rapporten. Uden brand-exclusions ligner PMax en helt fra, mens den delvist bare høster eksisterende efterspørgsel.
01Why PMax looks better than it is
Left to its own devices, Performance Max gravitates toward the easy and cheap: brand searches and bestsellers, where conversion rates are high. The problem is that most of that demand already existed — PMax doesn't create it, it harvests it, then takes the credit in the report. The result is an inflated PMax ROAS and an undervalued prospecting effort.
The fix is to build guardrails: brand exclusions so PMax stops bidding on brand searches, a separate brand campaign, and judging PMax on incrementality and MER instead of attributed ROAS. Otherwise you shift budget toward what looks best rather than what actually drives growth.
Frequently asked questions
How do I avoid PMax cannibalization?+
Exclude brand searches from Performance Max (brand exclusions) or run a separate brand campaign, and judge PMax on incrementality and MER instead of attributed ROAS. That way you see the real, created value rather than harvested demand.
Does cannibalization mean I shouldn't use PMax?+
No — PMax is effective when it's controlled. The problem isn't the campaign type, it's letting it run without guardrails. With brand exclusions and a profit signal, it becomes a powerful tool rather than a flattering report.
Related terms
Glossary
What is Performance Max (PMax)?
Performance Max (PMax) is a Google campaign type that runs across all of Google's inventory — Search, Shopping, YouTube, Display, Gmail and Maps — steered by one algorithm toward a single conversion goal.
Read the entry →Glossary
What are brand vs generic searches?
Brand searches are searches that contain your name (people who already know you). Generic (non-brand) searches are category and product searches from people who haven't yet chosen you.
Read the entry →Glossary
What is incrementality?
Incrementality is the added effect a marketing effort creates: the sales that happened only because the ad ran. Sales you'd have gotten anyway aren't incremental — whatever the platform credits.
Read the entry →Glossary
What is MER?
MER (Marketing Efficiency Ratio) is your total revenue divided by your total marketing spend across every channel. It ignores the platforms' own attribution and shows how efficiently the whole marketing machine is working.
Read the entry →
Malthe Weibeck Thomsen
Growth Hacker · Senior Pull Specialist at Oaksmond
Pull specialist with 8+ years' experience. Comes from the agency world and has since worked as an independent consultant for several of the country's largest brands.
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