To design ionic liquids (ILs) as effective liquid absorbents for CO2 separation from flue or synthesis gases, it is necessary to know the properties and phase equilibria of the CO2/IL systems. The molar volumes of CO2/IL mixtures are predicted with the heterosegmented statistical associating fluid theory equation of state. The comparison with the available experimental data shows that the model can be used to predict reliably the molar volumes of COAL mixtures from 293 to 413K and pressures up to 160 bar. In addition, the partial molar volume of CO2 in CO2/IL mixtures and the partial molar volume of CO2 at infinite dilution in an IL are also predicted. (C) 2011 Elsevier B.V. All rights reserved.