The effects of various extraction conditions on the dynamic extraction of the essential oil components carvone and limonene from spearmint leaves using SC-CO2 were investigated. The extraction rate increased with increasing pressure or decreasing temperature. An increase of the CO2 flow rate increased the extraction rate but decreased the solvent efficiency of CO2. Ground leaf samples with a smaller particle size showed an enhanced initial extraction rate for carvone as compared to larger particle size leaf samples. The use of an ethanol modifier did not enhance the extraction rate but did cause the coextraction of pigment and waxy substances.