The content and composition of fatty acids and sterols in the seed oil of two cultivated evening primrose species (Oenothera paradoxa Hudziok, O. glazioviana Micheli in Mart.) and two willow herb species (Epilobium tetragonum L., E. hirsutum L.) were compared. A GC analysis of the evening primrose seed oil resulted in identifying five fatty acids (palmitic, stearic, oleic, linoleic, and gamma-linolenic acids), with linoleic and gamma-linolenic acids as dominant compounds. In the willow herb seed oil six fatty acids were identified (palmitic, stearic, oleic, linoleic, gamma-linolenic and alfa-linolenic acids) with palmitic and linoleic acids as dominant compounds. An HPLC analysis indicated the presence of four free sterols in the evening primrose seed oil and five in the willow herb seed oil. beta-Sitosterol and brassicasterol appeared to be the main sterols in seed oils of the investigated species.