CO2 adsorption capacity of zeolite 13X and Na+-chabazite at 473 K was estimated by extrapolating the CO2 adsorption isotherm data measured in the temperature range of 298 to 373 K by employing the Clausius.Clapeyron equation, and compared with those by gravimetric measurements using a TGA unit and by the breakthrough curves obtained using a gas mixture (CO2 30% in N2 balance) in a fixed bed adsorption unit. All three methods produced comparable CO2 adsorption capacities, and justified the suggested experimental approach of the extrapolation procedure using the low temperature isotherm data for estimating gas adsorption capacity at high temperature conditions.