Abstract The water distilled volatile oils from aerial parts of fruits of Carum copticum (L.) C. B. Clarke in Benth. et Hook. and aerial parts of Semenovia tragioides (Boiss.) Manden., two Umbelliferae species of Iran, were analyzed by GC, GC/MS and 1H-NMR spectra of the main compounds. The aerial parts and fruits volatile oils of C. copticum were found to contain thymol (42.7% and 46.2%), Î³-terpinene (38.5% and 35.9%) and p-cymene (14.1% and 13.9%) as main components. p-Cymene (20.5%), (Z)-Î²-ocimene (9.7%) and cinnamyl isovalerate (9.4%) were the main components in the oil of S. tragioides. The structures of thymol, Î³-terpinene and p-cymene were confirmed by their 1H-NMR spectra.