The surface effects on the isotropic-nematic phase transition are analyzed using a functional form of the surface energy which contains two terms : one linear term in the order parameter and the second proportional to the square of the order parameter. The first-order nematic-paranematic phase transition is found to take place only in limited ranges of substrate potential strengths. This transition is examined for p-azoxy-anisole (PAA) in the framework of "the hard ellipsoids in an anisotropic mean field" model.