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 ([C2mim][Tf2N]) and CO2+1-methyl-3-pentyl-imidazolium bis(trifluoromethylsulfonyl)imide ([C5mim][Tf2N]) at temperatures up to 363K and pressures up to 50MPa. 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.