Volatiles from the essential oil of the liverwort Conocephalum conicum were analysed. The chirality of the monoterpene hydrocarbons was studied by two-dimensional ps chromatography. All compounds except beta-phellandrene showed high optical purity. For the identification of enantiomers, (+)-beta-phellandrene and (-)-alpha-thujene were prepared from (+)-limonene and (+)-sabinene, respectively.