Abstract: Techniques are described for selecting content items in various manners, such as by selecting product-related content items for display to consumer users. The content items may include advertisements or other promotional materials, and the selecting may be performed as part of determining particular promotional materials to display to particular users in particular situations, such as to accompany search results. In addition, the selecting of particular content items may be based on categorization of products indicated in search results and/or based on search terms used in searches performed on retail web sites. Particular content items are then selected based on the categorization, which may be for products distinct from those indicated in the search results, and may then be displayed with or otherwise in association with the search results.