Removal of acid gases is an important step of natural gases and industrial gas streams processing both from the economical and environmental of view. Aqueous solutions of alkanolamines are well known to be efficient chemical solvents for the CO2 capture. Reliable experimental data for solubility and enthalpy of solution of acid gases in aqueous solutions of alkanolamines are required for the design of gas treating equipments and to develop thermodynamic models describing this process. In this work a rigorous model to correlate both the solubility and the enthalpy of solution of CO2 in the absorbent solution is presented. It is based on a system of equations for the chemical and phase equilibria. The activity coefficients of both molecular and ionic species in the liquid phase are calculated from a modified Pitzer equation [1] and the fugacity coefficients in the vapor phase using a truncated Virial equation of state. The equilibrium constants for the chemical reactions and the Henry's law constant are obtained from different literature sources [2,3]. Selected interaction parameters in modified Pitzer equation are regressed from experimental and literature solubility data using the MINUIT code [4]. The enthalpies of solution are calculated from this model by temperature derivation of the equilibrium equations. The model is tested by comparing calculated enthalpies of solution with experimental enthalpies of solution in 15 and 30 wt% aqueous solutions of monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), 2-Amino-2-Methyl-1-Propanol (AMP) [5] and methyldiethanolamine (MDEA) [6]. The importance of the different enthalpic contributions associated to chemical reactions and physical equilibria will be discussed.