Performance Max was supposed to be the future: one campaign, all channels, fully automated. Instead, you're staring at declining performance, no visibility into what's happening, and a growing suspicion that something is deeply wrong.
You're probably right.
The Three Ways PMAX Fails
1. The Budget Black Hole
PMAX combines Search, Shopping, Display, YouTube, Gmail, and Discover into one campaign. The problem is you can't see where budget is actually going.
We audit accounts where 40%+ of PMAX spend is going to Display placements—low-intent, low-conversion inventory that looks like retargeting but performs like brand awareness.
Meanwhile, high-intent Shopping traffic is being starved of budget.
The symptom: Spend goes up, conversions stay flat, and you have no idea why.
2. Brand Cannibalisation
PMAX loves brand traffic. It's easy to convert. It makes the algorithm look good.
The problem: you were already going to get those conversions. You're paying for traffic you owned for free.
In some accounts, 30-40% of PMAX conversions come from branded searches. Strip those out and the campaign economics look very different.
The symptom: "Great" PMAX ROAS but overall account efficiency is declining.
3. Asset Group Confusion
Google recommends creating "themes" in your asset groups. Most advertisers interpret this as one or two asset groups covering everything.
The result: mixed signals. Google doesn't know whether to optimise for your £20 accessories or your £500 furniture. It defaults to what converts easily—usually not what you want to sell.
The symptom: Wrong products getting traffic. Best margins ignored.
How To Diagnose Your PMAX Problem
Step 1: Pull the Placement Report
Using scripts or third-party tools, extract where your PMAX budget is actually going. If more than 20% is on Display/YouTube and you're an ecommerce brand, that's a red flag.
Step 2: Check Brand Exposure
Use the Search Terms insight (limited, but available) to estimate brand term exposure. If brand terms are driving most conversions, your true PMAX performance is much worse than reported.
Step 3: Audit Asset Groups
Do your asset groups align with commercial intent? Are high-margin products in their own asset group with appropriate bidding, or are they mixed with everything else?
Step 4: Compare to Standard Shopping
If you're running Standard Shopping alongside PMAX, compare performance. Often, Shopping outperforms when you isolate for non-brand traffic.
When PMAX Actually Works
PMAX can work well when:
- You have strong creative assets (it needs good inputs)
- Asset groups are segmented by commercial intent
- Brand is excluded or properly controlled
- You have sufficient conversion volume for the algorithm to learn
- You monitor placement distribution, not just top-line ROAS
The problem is most accounts don't meet these conditions. They set up PMAX based on Google's defaults and hope for the best.
What To Do Next
- Get visibility into placement distribution
- Estimate brand traffic percentage
- Review asset group structure against commercial priorities
- Consider testing Standard Shopping for high-priority products
If you've been running PMAX for 6+ months without auditing it, there's almost certainly hidden waste.
Want us to look inside your PMAX? Book a PMAX audit discovery call and we'll show you where budget is actually going.