The surface excess amounts of supercritical carbon dioxide (SC-CO2) on NaY-type zeolite were measured by an isochoric method at 308.2 K. The adsorption amounts of 2,6- and 2,7-dimethylnaphthalene (DMN) isomers dissolved in SC-CO2 were also measured at 308.2 K by an isochoric method with an ultraviolet detector. The surface excess amounts Of CO2 show a maximum value near the critical pressure Of CO2 and then markedly decrease with increasing pressure and eventually become constant at high pressure. The adsorption amounts of 2,6- and 2,7-DMN gradually decrease with increasing total pressure. The adsorption amounts of 2,7-DMN are about six times higher than those of 2,6-DMN. The separation coefficients in supercritical CO2 are much higher than those in liquid octane and ethanol. The experimental data were correlated by an extended Radke-Prausnitz equation. The correlated results are in good agreement with the experimental data.