In this work, a tin oxide film was prepared on a silicon wafer. It has exhibited the typical behaviour of a metal-oxide-semiconductor (MOS) structure. This MOS structure was stressed with Co-60-gamma radiation in the total dose range of 0-500 kGy at room temperature. The effects of the Co-60 gamma radiation on the following properties of Au/SnO2/n-Si (MOS) structures, have been determined before and after irradiation: dielectric constant (epsilon'), imaginary dielectric constant (epsilon''), dielectric loss tangent (tan delta) and AC conductivity (sigma(AC)). The values of epsilon', epsilon'', tan delta and sigma(AC) show a strong dependence on the applied voltage and radiation dose. Additionally, the dielectric properties of MOS structures have been found to be strongly influenced by the presence of dominant radiation-induced defects. Experimental results show that the interfacial polarization contributes to the improvement of the dielectric properties of Au/SnO2/n-Si (MOS) structures. The capacitance and conductance measurements are corrected for series resistance before and after irradiation. (C) 2008 Elsevier B.V. All rights reserved.