Hydroxycinnamates including free hydroxycinnamic acids and their chlorogenic acid derivatives and glycosides have been profiled in leaf extracts of 98 Rhododendron species using LC-MS techniques. In total, 69 hydroxycinnamic acid derivatives were identified in the leaves of 98 Rhododendron species. Some derivatives serve as unique phytochemical marker for a single species, whereas other compounds are limited to certain subgenera. The distribution of compounds among six different subgenera of Rhododendron was studied using PCA and PLS-DA. This contribution presents data that provide unique metabolomic insight in the distribution of a class of secondary metabolites within a large selection of species from the botanically diverse plant genus Rhododendron.