Adsorption behaviors (adsorption coefficient, intraparticle effective diffusion coefficient, and axial dispersion coefficient) of benzene and 2,6- and 2,7-dimethylnaphthalene (DMN) on NaY-type zeolite in supercritical carbon dioxide were studied by impulse response analysis. The experiments were performed at temperatures of 308.2, 318.2, and 328.2 K and pressures of 12.0, 14.8, and 19.8 MPa. It was found that larger adsorption coefficients for benzene and 2,6- and 2,7-DMN are obtained at lower pressure and higher temperature and that larger intraparticle effective diffusion coefficients and the larger axial dispersion coefficients for all systems are obtained at higher temperature. However, it was shown that pressure little affects the intraparticle effective diffusion coefficients and the axial dispersion coefficients. The adsorption coefficients for 2,7-DMN are larger than those for 2,6-DMN and the intraparticle effective diffusion coefficients for 2,7-DMN are almost the same as those for 2,6-DMN.