(Liquid + liquid) equilibrium (LLE) data for {1-methyl-3-octylimidazolium bis[trifluoromethylsulfonyl]imide + thiophene + n-dodecane} and {1-methyl-3-octylimidazolium bis[trifluoromethylsulfonyl]imide + thiophene + cyclohexane} ternary systems have been determined experimentally at 298.15 K. The compositions of the tie-lines ends have been obtained by gas chromatographic analysis of phases at equilibrium, being distribution coefficients and separation factors calculated from them. The experimental results have been correlated by means of the NRTL model but considerable deviations from experimental data were found. (C) 2007 Elsevier Ltd. All rights reserved.