The use of antifoaming and corrosion inhibitor agents to prevent foaming and corrosion, respectively, is widely used in the carbon dioxide (CO2) absorption process using alkanolamines. However, the effect of these agents on the capacity of the alkanolamine solutions to absorb CO2 is unknown. We present a study on the phase equilibria and solubility of CO2 in mixtures of aqueous methyldiethanolamine (MDEA) solutions with and without these additives and show how the liquid phase properties and CO2 loading capacity is affected.