In this work, the phase behaviour of the binary system of carbon dioxide and the ionic liquid 1-ethyl-3-methyl imidazolium bis(trifluoromethylsulfonyl)imide ([emim][Tf2N]) has been studied experimentally. The equipment used for the experiments is the Cailletet set-up, based on visual observations of phase transitions of systems with constant overall composition. Results are reported for carbon dioxide concentrations ranging from 12.3 to 59.3 mol%, and within temperature and pressure ranges of 310-450 K and 0-15 MPa, respectively. The data reveal an extremely high capacity of the selected ionic liquid for dissolving CO2 gas, for example, reaching up to about 60 mol% within the above-mentioned pressure and temperature range. Also, the solubility Of CO2 in the ionic liquid [emim][Tf2N] is compared to the solubility Of CO2 in the ionic liquid [emim][PF6], an ionic liquid that shares the same cation. (c) 2007 Elsevier B.V. All rights reserved.