The diffusion and adsorption of CO2 inside the pores of Li, Na, and K ion-exchanged X-type zeolites were simulated by molecular dynamics and Monte Carlo calculations. Carbon dioxide diffused inside the zeolites pores while it was colliding with pore walls. Then it stayed in a super cage of zeolites. Inside the pore of Li+ ion-exchanged X-type zeolite (Li-X), the electrostatic potential term was -570 kcal/mol, this value was considerably smaller than those of CO2 inside the pores of Na-X and K-X. On the other hand, from Monte Carlo calculations, CO2 was found to strongly absorb near the 3B site for Li+ ions. When CO2 passed through the pores of alkali ion-exchanged X-type zeolites, the interaction between the CO2 molecule and the 3B site for Li cation was fairly large.