Response Surface Methodology was used to determine the effects of solvent flow rate (1, 3 and 5 g/ min), pressure (300, 375 and 450 bar) and temperature (40, 50 and 60 degreesC) on hazelnut oil yield in supercritical carbon dioxide (SC-CO2). Oil yield was represented by a second order response surface equation (R-2 = 0.997) using Box-Bhenken design of experiments. Oil yield increased with increasing SC-CO2 flow rate, pressure and temperature. The maximum oil yield was predicted from the response surface equation as 0.19 g oil/g hazelnut (34% of initial oil) when 4 g hazelnut particles (particle diameter < 0.85 mm) were extracted with 5 g/min SC-CO2 flow rate at 450 bar, and 60 degreesC for 10 min. Total extraction time at these conditions was predicted to be 35 min.