Effects of process parameters on extraction of rosemary on with supercritical carbon dioxide were investigated. The parameters included particle size (mean particle diameter <150-436.38 mu m), solvent flow rate (1-5 g/min), pressure (100-180 bar), temperature (40-60 degrees C) and ethanol addition to the material (3 wt.%). A two-stage separators procedure was used to induce the fractional separation of the extracts. The Sovova's model was used to describe the extraction process. The hardly accessible solute x(k) and the volume mass transfer coefficients in the fluid phase (k(f)a) and solid phase (k(s)a) were used as fitting parameters. The maximum average deviation between measured and calculated oil yield was 7.6%. Mass transfer coefficients in the fluid phase and solid phase varied between 0.6 and 2.8 x 10(-2) s(-1) and between 8.3 and 11.7 x 10(-5) s(-1), respectively. (C) 2009 Elsevier B.V. All rights reserved.