Does PMax always cannibalize Search campaigns?

No. PMax and Search can coexist without cannibalization if they target different query types and audiences. Cannibalization only occurs when PMax competes for the exact same queries as dedicated Search campaigns. With proper brand exclusions and structure, PMax can focus on prospecting while Search handles branded and high-intent non-brand queries.

Can PMax and Search campaigns serve on the same query simultaneously?

Not exactly the same impression, but both campaigns can compete in the same auctions. Google's auction system determines which campaign wins, but generally PMax takes priority when Google predicts it will achieve the campaign's goals better. This means brand Search impression share can decline when PMax is active on the same terms.

What should I check in Search Terms Insights for PMax?

Search Terms Insights shows query categories that PMax is serving on, including brand terms, competitor terms, and category queries. Look for a high percentage of brand-term conversions or impressions. If brand terms are significant, PMax is likely overlapping with your brand Search campaign and should either have brand exclusions or be tested separately.

Should I always separate PMax and brand Search campaigns?

Structural separation helps prevent cannibalization, but the key decision is whether to add brand exclusions to PMax rather than run completely separate campaigns. If you have a strong brand Search campaign, add brand exclusions to PMax so both campaigns can run without overlap. This lets you keep a single PMax for prospecting while brand Search captures branded queries efficiently.

Performance Max Search Cannibalization Audit: Find and Fix Overlap

What is Performance Max search cannibalization?

Performance Max cannibalization occurs when a PMax campaign serves on search queries that are also being targeted by existing Search campaigns, particularly brand and non-brand Search. Because PMax generally takes priority in auctions when Google determines it can better achieve campaign goals, it can absorb impressions and conversion credit from Search campaigns without adding new reach.

How can PMax overlap with Search campaigns?

PMax has access to Search inventory without using keywords. It uses signals from asset groups, audience data, and conversion history to decide when to serve. If PMax is competing for the same queries as your brand or high-intent non-brand Search campaigns, it may claim conversions at a higher cost than the dedicated Search campaign would have. This overlap happens silently unless you actively look for it.

How do you spot brand query cannibalization?

Check Search Terms Insights within the PMax campaign reporting. If brand terms are appearing in the category breakdown, PMax is serving on branded queries. Also check your brand Search campaign impression share. A declining impression share combined with PMax volume increasing on branded terms often indicates cannibalization. Compare the trends month over month to confirm the pattern.

What report should you check first?

Start with PMax Search Terms Insights in the Insights tab. This shows query categories that PMax is serving on. Then check brand Search campaign impression share trends over the same period. If brand impression share is declining while PMax conversions are growing, the pattern warrants investigation. These two reports together tell you whether overlap exists.

What is the difference between cannibalization and healthy coverage?

Healthy coverage means PMax and Search serve on different queries and different audiences, each adding reach the other cannot. Cannibalization means PMax is serving on queries that already had efficient Search coverage, adding cost without adding incremental conversions. The distinction requires looking at conversion cost comparison and whether Search impression share dropped when PMax increased.

Symptom	Likely Cause	Where To Check	Next Action
Brand Search campaign impression share declining	PMax serving on brand terms	Brand Search IS report + PMax Search Terms Insights	Add brand exclusions to PMax, test impact
PMax ROAS rising while non-brand Search stagnates	PMax absorbing brand credit	Segmented ROAS by campaign type	Run brand exclusion test
CPC on brand Search rising with no new competitors	PMax bidding against own brand Search campaign	Auction Insights report for brand Search	Add brand exclusions to PMax
Total account conversions flat despite PMax scale	PMax redistributing existing demand, not generating new	Compare total account conversions before/after PMax launch	Incrementality test
Shopping campaign CPCs rising	PMax taking Shopping inventory	Shopping IS report	Restructure PMax product groups and review Shopping exclusions

Check 1: Query overlap

–Review PMax Search Terms Insights for brand term categories
–Compare brand Search campaign impression share before and after PMax launch
–Look for non-brand high-intent terms appearing in PMax Search Terms Insights

Check 2: Conversion credit review

–Compare brand Search conversion volume month over month since PMax launch
–Check whether total account conversions increased or just redistributed
–Segment by campaign type to see where conversions shifted

Check 3: Cost efficiency

–Compare CPA for brand Search vs PMax for the same query categories
–Look for CPA increases in brand Search that coincide with PMax growth

Check 4: Structural fixes

–Are brand exclusions applied to PMax?
–Is there a dedicated brand Search campaign with adequate budget?
–Are non-brand high-performing keyword themes excluded from PMax via negative keyword lists (where supported)?

PMax campaign-level negative keyword lists have limited support compared to standard Search campaigns. Where available, apply shared negative keyword lists to prevent PMax from serving on queries that have dedicated Search campaigns. Confirm the current capability in your Google Ads account, as features may vary by account type.

For practical steps on fixing brand overlap, see our guide on brand exclusions. For measuring whether PMax is truly incremental, check our incrementality testing guide.

Performance Max Search Cannibalization Audit: How To Find and Fix Campaign Overlap