Ionic liquids with their limitless combination of cations and anions can offer an optimal solvent for a specific purpose. But not all. corresponding experimental studies are possible as they will be time consuming and expensive. A judicious screening of the various possible solvents is required to select the proper ionic liquid. Conductor-like screening model (COSMO) along with its extension to real solvents can be used for these predictions. In this work, modified version COSMO_LL has been used to predict the liquid-liquid equilibria (LLE) for 32 ternary systems, available in literature, each having an ionic liquid. A complete dissociation of cations and anions of the ionic liquid has been assumed. The root mean square deviation for all these systems is similar to 9% which is excellent when compared with similar to 50% obtained for predictions using the nondissociated composite molecule. Additionally, experimental LLE. data has been collected for four ternary systems, namely: (a) 1-ethyl-3-methylimidazolium ethylsulphate [Emim] [EtSO4] - Ethanol-Hexene, (b) 1-ethyl-3-methylimidazolium ethylsulphate [Emim] [EtSO4] - Ethanol-Heptene, (c) 1,2-dimethyl-3-ethylimidazolium ethylsulphate [E-2,3-dmim] [EtSO4] Ethanol-Hexene, and (d) 1,2-dimethyl-3-ethylimidazolium ethylsulphate [E-2,3-dmim] [EtSO4] - Ethanol-Heptene. The tie lines have been estimated using NMR and these have been compared with COSMO_LL predictions giving an average rmsd of similar to 6%. (C) 2008 American Institute of Chemical Engineers.