Abstract Essential oils from three collections of Ducrosia assadii Alava. were obtained by a commercial-scale hydrodistillation. The oils were analyzed by capillary gas chromatography, using flame ionization (GC/FID) and capillary gas chromatography mass spectrometry (GC/MS) detection. Sixty-one components were identified in the first oil of D. assadii from Lalehzar with decanal (74.0%), dodecanal (7.2 %) and Î±-pinene (4.0%) as the main constituents. Fifty components were identified in a second oil of D. assadii from Lalehzar with decanal (35.2%), nonadecane (12%) and citronellyl acetate (11.6%) as the main constituents. The oil from Dehbakrii also contained decanal (36.4%) as the main component of an oil recovered from the distillate water. The results showed that the amount of decanal is remarkably high in the oils of D. assadii.