-y and electron as grown crystals were used while for proton irradiations the crystals were thermally annealed. For small concentrations of cerium ions (u 0.01 at.%) an increase in the lumi- nescence (about 100%) was observed after gamma irradiation with a dose of 10 5 Gy. This increase was due to the growth in Ce 3 + ions concentration after γ-irradiation (= 50%), due to the Ce 4 + -> Ce 3reaction. For highly doped Ce:YAG crystals (0.1 at%, 0.2 at.%) also an increase, but much smaller (4%), for the Mg codoped crystals (0.1 at.%) was observed. After 1 MeV electron irradiation in the over-threshold type interaction a de- crease in luminescence is observed due to the domination of the Ce3+ -> C e4+ ionization process. In the case of the proton irradiation, for small fluencies (Pe. 10 13 particles/cm 2 ) an increase in luminescence is observed due to the domination of the recharging processes of Ce