Solubility data of carbon dioxide (CO(2)) in the ionic liquids 1-alkyl-3-methylimidazolium trifluoromethanesulfonate ([C(n)mim][TfO]; n = 2, 4, 6, 8) are presented at pressures up to about 40 MPa and at temperatures between (303.85 and 344.55) K. The equilibrium pressure increased very steeply at high CO(2) concentrations. The solubility of CO(2) in the ionic liquids decreased with an increase in temperature. The CO(2) solubility increased with the increase in the alkyl chain length on the cation of the ionic liquids. The phase equilibrium data for the CO(2) + ionic liquid systems have been correlated using the Peng-Robinson equation of state.