Co-selected images are labeled based on a topic score that is a measure of relevance of the co-selected image to a first topic to which a reference image belongs. The first topic to which the reference image belongs is identified based on a reference label associated with the reference image. The co-selected images are images that are selected for presentation subsequent to selection of the reference image during a user session. The co-selected images are identified based on selection data for user sessions in which the reference image was selected for presentation. The topic score is generated based on a frequency of selection of the co-selected image. Image search results for a second topic can be filtered to remove images that are labeled as belonging to the first topic or the image search results can be reordered to adjust the presentation positions at which images are referenced based on the topic to which the images belong.