In this study, polyethersulfone (PES) membrane was subjected to surface modification using hexamethyldisiloxane (HMDSO) and 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) in radio frequency (RF) plasma system to improve its hydrophobic property for recovery of waste frying oil. Structural and morphological changes on the membrane surfaces were characterized by contact angle measurements, Fourier transform infrared spectroscopy-attenuated total reflection (FTIR-ATR) and atomic force microscopy (AFM). Permeate fluxes, physical and chemical properties of waste frying oil and waste frying oil-methanol micella (oil/methanol 1/3, 1/1, 1/3, v/v) after filtration through unmodified and modified PES membranes were investigated. The results showed that PES membranes modified with HMDSO at 75 W for 5 min (discharge power-exposure time) selectively rejected total polar compounds (TPC) and free fatty acids (FFAs) of waste frying oil to the extent of 46.9-48% and 35.3-40%, respectively. Furthermore, the viscosity of waste frying oil was reduced to the extent of 9.4-12.8%. RF-plasma-treated PES membranes appeared to improve the regeneration of waste frying oils and allow these oils to be used for either repeated frying operations or biodiesel production. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 123: 3402-3411, 2012