Electrical properties of undoped epi-layers of n-GaN subjected to gamma-irradiation and annealing are investigated by means of Hall effect measurements and DLTS spectroscopy. Despite slight changes in the concentration of charge carriers in the studied materials, the behavior of the electron mobility points to the presence of radiation-induced defects in appreciable concentrations. DLTS spectra revealed three electron traps E(C)-E(1) approximate to0.25 eV, E(C)-E(2) approximate to0.58 eV, and E(C)-E(3) =0.81 eV in the initial layers and two major traps E(C)-E(4) approximate to0.15 eV and E(C)-E(5) =0.95 eV in the irradiated n-GaN. The parameters of there traps were determined. Both radiation-induced traps were annealed out at T=450 degreesC. In addition the traps E(C)-E(1) and E(C)-E(2) changed in concentrations upon annealing, as well.