Properties of Porous Silicon (PS) subjected to gamma irradiation in an air ambient and in vacuum have been studied. Gamma-irradiation was carried out in usual room atmosphere, and in evacuated tubes. The samples of porous silicon were investigated by means of photoluminescence (PL) and infrared (IR) absorption. For the samples irradiated under atmospheric conditions, the PL intensity increases by several times as the dose increases up to 1019photons/cm2 and after that point it starts to go down. For a dose of ˜9.1019photons/cm2 the PL intensity falls by a factor of ˜50. The position of the spectrum maximum does not change, but the half-width of the spectrum increases by 2 or 3 times. In the case of gamma-irradiation in vacuum the PL intensity gradually decreases with increasing dose. IR absorption measurements showed variations of the intensity of Si-H and Si-O bands with the irradiation dose. Enhancement of PL at lower doses has been explained by irradiation assisted oxidation of PS at atmospheric conditions and its degradation at higher doses by suppresion of the light-emitting centers.