The optimization of temperature and pressure conditions for the extraction of n-octadecane with supercritical CO2 has been investigated. This work presents experimental phase equilibria results of the study carried out at supercritical conditions for the System CO2+n-octadecane in the temperature range 310-353 K, and in the pressure range 10-20 MPa. The experimental work was carried out in a semi flow-type apparatus constructed in our laboratory, the amount of the extracted solute was determined gravimetrically. The equipment and experimental procedure were tested by performing measurements of the solubility of n-decane in supercritical CO2 at 344.15 K, and the solubility of n-hexadecane in the same solvent at 308.15 K. The solubility of n-octadecane in supercritical CO2 increases as the pressure increases but the functionality with temperature shows a maximum solubility value at 313 K. The system pressure was measured to +/-2 kPa, temperature was measured to +/-0.05 K and the composition was determined to +/-0.0002 in mole fraction.