This work focuses on the extension of group parameters of the UNIFAC model to systems with ionic liquids. The new group parameters for ionic liquids were obtained by means of correlating the activity coefficients of solutes at infinite dilution in ionic liquids at different temperatures. The group parameters for 12 main groups and 24 subgroups were added into the current UNIFAC parameter matrix. It was verified that the new group parameters can be used not only for predicting the vapor−liquid equilibria of the systems with ionic liquids at finite concentration, but also for screening the suitable ionic liquids in separation processes. Since there have been only a limited number of functional groups for ionic liquids included in the UNIFAC model, the future development of this predictive model will still require much more accurate experimental data.