The kinetics of CO2 absorption by aqueous solutions of methyl diethanol amine (MDEA) were measured in the temperature range (296-343) K and MDEA concentration range (830-4380) mol . m(-3) (10-50 mass %). A thermoregulated constant interfacial area Lewis-type cell was operated by recording the pressure drop during batch absorption. The kinetic results are in agreement with a fast regime of absorption according to film theory. MDEA depletion at the interface has a significant effect on the kinetics at the CO2 pressures (100 to 200 kPa) studied in this work, especially at low temperatures and low MDEA concentrations. Considering only the reaction between CO2 and MDEA, the CO2 absorption appears as a first-order reaction with respect to MDEA. The activation energy found for the reaction between CO2 and MDEA is 45 kJ . mol(-1), but this value depends significantly (by about 10% in the worst case) on the vapor-liquid equilibrium data used.