A computer system, computer program, and related methods product for selecting one or more targeted advertisements to be displayed along with a set of search results. In general, a computer system and database storage system store one or more campaigns associated with a set of documents and at least one advertisement. The computer system is programmed with an ad targeting module to: identify all campaigns that have at least one document relating to a search result set; analyze the search results set to calculate at least one intersection score between the search result set and at least one of the one or more campaigns; select a matching campaign from the one or more campaigns based on the at least one intersection score, select at least one advertisement from the matching campaign; and cause the at least one advertisement selected from the matching campaign to be displayed with the search result set.