An experimental study has been carried out to investigate the characteristics of facilitated transport of CO2 through hydrophilic polymeric membranes with an immobilized aqueous potassium carbonate solution. The rate of permeation for CO2 increased with increasing K2CO3 concentration, decreasing membrane thickness, and decreasing CO2 partial pressure. The permeation rate for CO2 was predicted by a theoretical model based on mass transfer accompanied by a reversible chemical reaction. such as hydration reaction of CO2, reaction of CO2 with OH-, or dissociation of HCO3-. The permeation rate for CO2 increased by adding K2SO3, PEG, or DBC to the aqueous K2CO3 solution. By assuming that these additives enhanced the hydration reaction of CO2, the forward-reaction rate constant was estimated by fitting to the experimental R-A. The values estimated thus were 1.35, 0.98, and 0.56 s(-1), for K2SO4, polyethyleneglycol, and Dibenzo-18-crown-6, respectively. These values amount to 15-36 times as large as those without additives.