Similar search queries and images

Methods, systems and apparatus, including computer programs encoded on a computer storage medium, for determining similar queries for image searches. In one aspect, a method includes generating, for each of a plurality of search queries, a selection vector for the search query, each selection vector including a plurality of vector elements, each vector element corresponding to a unique image, and the value of each vector element being proportional to a number of selections of its corresponding unique image in response to the unique image being presented as a search result for the search query. The method further includes selecting a first search query and a second search query from the plurality of search queries and determining, from the selection vectors for the first and second search queries, a similarity measure that is a measurement of the similarity of the first search query to the second query.