The damage induced in cerium dioxide or ceria by charged particle irradiations was investigated by various spectroscopic techniques, such as Raman spectroscopy, electron paramagnetic resonance (EPR) spectroscopy, and UV-visible absorption/reflection spectroscopy. These results confirmed the radiation resistance of this material which is not amorphised by heavy ion irradiations even for high fluence and high stopping power.  However, clear evidence of cerium reduction from the 4+ to 3+ oxidation state was provided by EPR and optical spectroscopy data after electron or heavy ion irradiations.