The solubilities of alpha-pinene and 1,8-cineole in supercritical carbon dioxide with and without cosolvent were measured by using a circulation type apparatus coupled with an on-line Fourier transform infrared (FT-IR) spectroscope at 323 K and 8.0 MPa. The cosolvents interested in this work were ethanol, water, acetone and hexane. The solubilities were measured under vapor-liquid two phases. The effects of cosolvents on the solubilities and selectivities of alpha-pinene and 1,8-cineole in supercritical CO2 were investigated. The selectivities at feed concentration of cosolvent of 0.056 mol L-1 were increased 1.23 times by ethanol and decreased 0.82 times by hexane. Peng-Robinson equation of state with a quadratic mixing rule was used for correlations of the solubilities for alpha-pinene and 1,8-cineole in supercritical CO2 with and without cosolvent. The correlated results reproduce the experimental data of cosolvent effects on the solubilities and selectivities of alpha-pinene and 1,8-cineole in supercritical CO2. (C) 2010 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.