New standards concerning environmental and safety issues are creating an increasing interest on ionic liquids as alternative solvents for a wide range of industrial applications. In this work, a new apparatus developed to measure vapor-liquid phase equilibrium in a wide range of pressures and temperatures was used to measure the phase behavior of the binary systems of carbon dioxide (CO2)+1-ethyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide ([C-2 mim][Tf2N]) and CO2+1-methyl-3-pentyl-imidazolium bis(trifluoromethylsulfonyl)imide ([C-5 mim][Tf2N]) at temperatures up to 363 K and pressures up to 50 MPa. A thermodynamic consistency test, developed for systems with incomplete PTxy data and based on the Gibbs-Duhem equation, was applied to the experimental data measured in this work and the Peng-Robinson EoS using the Wong-Sandler mixing rule was used to describe the experimental data with excellent results. (C) 2008 Elsevier B.V. All rights reserved.