The physical as well as the chemical solubility of carbon dioxide in several ionic liquids were predicted with quantum chemical a priori methods. The physical solubility was described with the model COSMO‐RS. The results were compared to experimental data. Both a qualitative and – based on the concept of relative solubility – quantitative benchmark for the solvents were possible. For the part of chemical absorption, the free reaction enthalpy, ΔRg, and reaction enthalpy, ΔRh, were determined with DFT calculations on the B3LYP/def2‐TZVPP level. By combining reaction and phase equilibrium, the CO2 loading of the reactive solvents were predicted. The results were validated with literature data. An approach was developed for a quantitative a priori description of both physical and chemical solvation of CO2.