The solubility of CO2 in a mixed nonaqueous solvent of methyldiethanolamine (MDEA) and methanol has been measured at 40 degrees C. The results are compared with the solubility of CO2 in pure methanol. The solubility of CO2 has also been obtained at 40 and 100 degrees C in an aqueous mixed solvent consisting of methanol (40 mass %), MDEA (40 mass %), and mater (20 mass %) at partial pressures of the acid gas up to 7.04 MPa. The solubility results are compared with the nonaqueous mixed solvent results and previously reported data for aqueous methyldiethimolamine.