In this work, we report a study on the liquid-liquid phase equilibria for N-methyl-2-pyrrolidone (NMP)+ hydrocarbon (n-hexane, n-octane, n-clecane, cyclohexame, cyclooctane, 2-methylpentane, 3-methylpentane, isooctane, 2,2-dimethylbutane and 2,3-dimethylbutane) and N-cyclohexyl-2-pyrrolidone (NCP) + water binary mixtures at ambient pressure. The studied systems, except NCP + water, present miscibility curves with upper critical solutions temperatures (UCSTs). The results for NMP+hydrocarbon mixtures are correlated using two different approaches: (i) NRTL and UNIQUAC semiempirical models and (ii) molecular-based equations of state (statistical associating fluid theory (SAFT) and perturbed-chain statistical associating fluid theory (PC-SAFT)). Accurate correlations are inferred for NRTL and UNIQUAC models whereas for SAFT and PC-SAFT EOS complex mixing rules are required to obtain accurate results. (C) 2008 Elsevier B.V. All rights reserved.