The effects of three operating conditions of supercritical CO2 extraction (SCE), namely pressure, temperature and time, on yield, chemical composition and antioxidant activity of lavender essential oil were investigated using a response surface method coupled with a central composite design. Pressure and time had a significant linear effect on both yield and antioxidant activity of extracts tested by the 1,1-diphenyl-2-picrylhydrazyl assay, while temperature had a lesser impact except for the effect of its interaction with pressure on extract yield. Generally, the yield and antioxidant activity of the extracts increased with pressure and time. However, antioxidant activity of extracts examined by the 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulphonic acid) assay was not affected by any operating conditions. In short, the extracts obtained at high pressure, high temperature and long extraction time had high yield and high antioxidant activities. The three operative parameters did not have any impacts on the chemical composition of the extracts. (C) 2012 Elsevier B.V. All rights reserved.