Isotherms of adsorption of CO2 on a Ta2O5 surface and the same surface coated with a 0.5 monolayer of PdCl2 were measured over temperature and pressure ranges of 293-473 K and 0.015-1.5 Pa, respectively. It was established that, in the presence of PdCl2, the adsorption becomes greater in value and reversible. The isotherms were S-shaped, which was explained by the association of adsorbed CO2 molecules due to the change in their polarization caused by rising CO 2 pressure. The influence of the temperature and PdCl2 on the adsorbate-adsorbate and adsorbate-adsorbent interaction constants were analyzed using the Kiselev isotherm and an isotherm that takes into account the interaction between the electrons of the semiconductor oxide and adsorbate molecules. © Nauka/Interperiodica 2006.