Which banner ad sizes account for the most click volume in the Google AdWords Display Network?

The definitive answer from Google in terms of impressions, as of 2011: http://static.googleusercontent.com/external_content/untrusted_dlcp/www.google.com/en//doubleclick/pdfs/display-business-trends-publisher-edition.pdf (see the chart on page 24) The top three ad units had such a large lead in impressions, it's reasonable to guess they had a similar lead in click volume. tl;dr = 300x250, 728x90, 160x600 So these are typically the ones you do first. After you have created one of each type (square-ish, horizontal, vertical) it's easier to create the other sizes later.

Based on the Google's latest data points, still 300x200 holds the highest CTR performance compared to any other format. Further, rich media ads are performing better than the regular images. Please have a look at the below chat for your reference. You can follow the below link which will help you useful insights on display advertisment. URL: http://www.richmediagallery.com/tools/benchmarks

I agree with Anna. I'm also getting a fairly consistent and healthy CTR with the 336x280. While it's not one of the universal 3 (160x600, 300x250 or 728x90), it is supported on GDN.

Here are the top 10 banner sizes ranked by impression share: 1. Medium Rectangle: 300×250 2. Leaderboard: 728×90 3. Wide Skyscraper: 160×600 4. Banner 468x60 5. Skyscraper 120x600 6. Rectangle 300x100 7. Micro Bar 88x31 8. Half-Page 300x600 9. Large Rectangle 336x280 10. Mobile Leaderboard 320x50 The top 3 banner sizes comprise nearly 80% of all served ad impressions. The top 10 combined make up 90% of all ad impressions. I've written a detailed article about the http://www.stefanmaescher.com/top10-banner-sizes/ including exact impression share percentages for each banner format.