For 5.0, 20.5, 50.0, and 75.0 mass % methyldiethanolamine (MDEA) aqueous solutions, solubilities of CO2 were measured at 323.15, 348.15, and 313.15 K, respectively. Isothermal absorption capacities of CO2 as a function of MDEA concentration are presented. Lastly, the absorption enthalpy of CO2 in 50.0 mass % MDEA solution was calculated to be 54 kJ.mol(-1) CO2.