This paper presents adsorption isotherm data of CO2 onto two different types of highly porous activated carbons (ACs) for temperatures ranging from (−18 to 80) °C and pressures up to 10 MPa. The assorted adsorbents are activated carbon fiber (ACF) of type A-20 and activated carbon powder of type Maxsorb III. Adsorption isotherm data have been obtained using a volumetric technique and fitted to the Dubinin−Astakhov (D−A), Toth, Langmuir, and modified D−A equations. The latter considers the pseudosaturation pressure of CO2 that plays an important role for supercritical gas adsorption, and the pseudosaturation pressure was determined from the experimental data. The Toth and modified D−A isotherms correlate with the experimental data within 5 % root-mean-square deviation (rmsd) and present a better fitting than that of the Langmuir and the D−A equations. The isosteric heat of adsorption data were derived from the Toth and modified D−A isotherm equations and the correlation proposed by Chakraborty et al., and ...