The dielectric anisotropy and dispersion of the real part of permittivity of 4-pentil-4'-cyanobiphenyl (5CB) were investigated in the relaxation frequency range from 10 MHz to 500 MHz. Two frequencies f(1) = 30 MHz and f(2) = 350 MHz characterizing the change of a sign of the dielectric anisotropy were obtained. The Debye relaxation fitting procedure showed that a quality of the fits was satisfactory in defining the frequency f(1), but there were discrepancies between the experimental and fitting results for the frequency f(2). It is due to the appearance of singularities on the dielectric spectrum around 300 MHz. The dielectric spectra are interpreted as a superposition of dielectric relaxation and resonance contribution. It was shown that isotropic phase and diluted solution of 5CB in benzene display the resonance dispersion region too.