The paper presents the results of electrical characterization of the interface and bulk properties of high-k Gd2O3 and Nd2O3 dielectrics epitaxially grown on silicon substrates. The limitations of the conductance technique for correct determination of the interface state density due to the presence of leakage currents through the dielectric are discussed. The charge carrier transport through the dielectric film was found to occur via the variable-range hopping conductance mechanism. The density of the interface states and their energy distribution for (100) and (111) Si orientation and the Gd2O3/Si and Nd2O3/Si interfaces were determined. The density and energy location of the bulk localized states in the band gap of the Gd2O3 and Nd2O3 dielectrics were estimated and a plausible nature of the observed defects was suggested.