The solubility of carbon dioxide in the ionic liquids 1-butyl-3-methylimidazolium hexafiuorophosphate and 1-nonyl-3-methylimidazolium hexafluorophosphate was measured at temperatures of 293.15 and 298.15K and pressure up to 4 MPa using a stoichiometric phase equilibrium apparatus. The measured data for 1-butyl-3-methylimidazolium hexafluorophosphate were in good agreement with existing literature data and new solubility data were reported for 1-nonyl-3-methylimidazolium hexafluorophosphate. The measured data were correlated using the group contribution non-random lattice fluid equation of state (GC-NLF EoS) proposed by Lee and co-workers. The group parameters for CG-NLF EoS were slightly modified at limited range to accommodate recent experimental data and better prediction at high pressure and long alkyl chains. (C) 2011 Elsevier B.V. All rights reserved.