CO 2 storage in geological formations hasbeen regarded as one of the promising methods to reduce anthropogenic CO 2 emissions. Among geological sequestration sites, un-mineable coal seams offer attractive sites because it can have a chance for the recovery of CH 4 from a coal seam (ECBM) in addition to CO 2 sequestration. Due to the higher adsorption affinity of CO 2 to coal, the injected CO 2 displaces the pre-adsorbed CH 4 being stored in the coal seams. To evaluate preferential CO 2 adsorptionon coals, adsorption and desorption behaviors of pure CO 2 and CH 4 on Kyungdong coal (anthracite coal, South Korea) were measured and competitive adsorption experiments with CO 2/CH 4 mixture gas were performed in this study. Adsorption behavior of anthracite with a significant amount of mineral matter was measured at 318 and 338 K up to 150 atm. To evaluate the moisture effect, a set of experiments on dry and wet coal was carried out by a volumetric method. The water dissolved in the CO 2-rich (or CH 4-rich) gas phase as well as coal swelling should be considered inevaluating the sorption capacity of a wet coal seam. In the mixture, the moleratio of CO 2 to CH 4 was lower in the equilibrium phasethan in the source gas at both temperatures throughout all pressures. It indicated the preferential CO 2 adsorption in competitive adsorption condition, and it could also be confirmed from higher CO 2 adsorbed amounts than CH 4 from the mixture. When the adsorption isotherms of mixture gas were compared with pure gas, those showed similar behaviors with pure CO 2 rather than CH 4.