The enthalpies of solution (Delta H-sol) of carbon dioxide (CO2) in two aqueous solutions (w = 0.1500 and w = 0.3000) of triethanolamine (TEA) have been measured for the first time at T = 322.5 K and 372.9 K and p up to 5 MPa, by flow calorimetry. Enthalpies of solution of CO2 (Delta H-sol) have been obtained as function of loading alpha (mol(CO2).mol(amine)(-1)). Solubility data (s) of the gas into the solution were also determined. Influences of temperature, pressure, and absorbent composition have been discussed. Our experimental enthalpies of solution have been compared with data derived from a thermodynamic model of phase equilibria based on a gamma-phi approach. The enthalpy of solution of CO2 in aqueous solutions of methyldiethanolamine (MDEA), monoethanolamine (MEA), and diethanolamine (DEA) have been compared to the present results to discuss the effects of the hindrance on the nitrogen nucleus as well as its degree of substitution, on the enthalpy of solution.