The group contribution lattice fluid equation of state (GCLF EOS) was first extended to predict the thermodynamic properties for carbon dioxide (CO2)-ionic liquid (IL) systems. The group interaction parameters of CO2 with IL groups were obtained by means of correlating the exhaustively collected experimental solubility data at high temperatures (above 278.15 K). New group parameters between CO2 and IL groups were added into the current parameter matrix. It was verified that GCLF EOS with two kinds of mixing rules could be used for predicting the CO2 solubility in ILs, and volume expansivity of ILs upon the addition of CO2, as well as identifying the new structure-property relation. Moreover, it is the first work on the measurement of the solubility of CO2 in ILs at low temperatures (below 278.15 K), manifesting the applicability of predictive GCLF EOS over a wider temperature range. (c) 2013 American Institute of Chemical Engineers AIChE J, 59: 4399-4412, 2013