You can track impressions only for banner ads and if your traffic source can place an impression pixel on their side (check with your traffic source manager).

If you fit these two conditions, follow these steps to track impressions:

1. When you create a traffic source you need to activate the "Track Impressions" checkbox.

2. Then, when setting up a campaign, choose the CPM model — this will display the impression pixel URL.

3. Place the impression pixel on the traffic source's side.

If placing an impression tracking pixel is not possible, you can only track visits, clicks, and conversions (without impressions).