The effect of Cu/Al molar ratio on the high-temperature adsorption characteristics of CO2 on the mixed oxides of Cu-Al hydrotalcite skeletal structure has been studied by thermogravimetry. The Cu/Al molar ratio of the hydrotalcites synthesized was varied between 1.0 and 3.0, and the adsorption temperature ranged from ambient to 600 °C. The hydrotalcite with Cu/Al molar ratio of 2.0 was found to be the most suitable adsorbent for high-temperature CO2 adsorption, in both the capacity and the rate of adsorption. The activation energy values suggested that the physical adsorption dominates at low temperatures (<400 °C) and the chemisorption dominates at high temperatures (>400 °C). © 2009 Akadémiai Kiadó, Budapest, Hungary.