abstract some new constituents were discovered in a very unusual spanish lavender: lavendula luisieri (rozeira) riv. mart. the essential oil of l. luisieri, which is produced on an industrial scale, was analyzed by a combination of gc and gc/ms. many components identified were irregular monoterpenoids, with a cyclopentanic structures unique in the plant kingdom, like -necrodyl acetate (20-25% of the oil) or -necrodol. the new structures identified were: 3,4,4-trimethyl-2-cyclohexen-1-one, 3,4,4-trimethyl-5-hexen-2-one, 2,3,4,5-tetramethyl-2-cyclopenten-1-one, 2,3,5,5-tetramethyl-4-methylene-2-cyclopenten-1-one, 1,1,2,3-tetramethyl-4-hydroxymethyl-2-cyclopentene, 2,4,5,5-tetramethyl-cyclopentadien-1,3-carboxylic acid and selina-4,7(11)-diene. a monoterpene whose exact structure remains unknown, is present in the oil at a level of (2-4%). other main compounds were 1,8-cineole and lavandulyl acetate.