In this work, we have studied the use of homologous imidazolium-based ionic liquids (i.e. with the same fluorinated and non-fluorinated anion) to perform the separation of an ether and an alcohol. Concretely, we have selected ethyl tert-butyl ether (ETBE) and ethanol due to the capital interest of their industrial separation. Liquid-liquid equilibrium (LLE) data for the ternary systems involved are presented. It has been found that 1-ethyl-3-methylimidazolium methanesulfonate leads to higher values of solute distribution ratios and selectivities than 1-ethyl-3-methylimidazolium trifluoromethanesulfonate, except for selectivity values at high solute concentrations. In addition, LLE data have been adequately correlated by means of the NRTL equation. (c) 2006 Elsevier B.V. All rights reserved.