A complementary item promoter user interface (UI) is provided that promotes, to a user, items that are complementary to an item of interest to the user. Upon the user's selection of an item of interest, the complementary item promoter UI presents a combination of complementary items selected in accordance with business rules data. The business rules data may be submitted by an administrative user to a content management service that deploys the complementary item promoter UI in a deployment environment. The business rules data may include rules that govern how complementary items are chosen or how they are to be displayed in the complementary item promoter UI.