Unlimited number of permutations with respect to cation and anion combinations of ionic liquids as well as large number of existed azeotropic mixtures cause experimentally impossibility to screen all of possible systems of these compounds. Therefore, predictive models have been developed as COnductor-like Screening MOdel for Real Solvents (COSMO-RS) - an a priori predictive method independent of experimental data, which only requires the information is the molecular structure of the compounds. In this work, COSMO-RS model has been used in prediction of activity coefficients at infinite dilution of about 60 different organic solutes and water in 12 ionic liquids as well as ternary liquid liquid equilibrium in 13 systems: (ionic liquid + methanol + heptane), (ionic liquid + thiophene + heptane) and (ionic liquid + benzothiophene + heptane). The model predictions are compared with experimental data (obtained in previously in our laboratory) in order to evaluate the accuracy of COSMO-RS model in phase equilibrium prediction of this kind of systems. (C) 2015 Elsevier B.V. All rights reserved.