The poor radiation hardness of the otherwise excellent x-ray storage phosphor CsBr:Eu2+ constitutes a problem for its commercial application in medical diagnostics. X-ray induced vacancy centers such as M-centers enhance the diffusion of Eu2+ activators resulting in a formation of photostimulated luminescence (PSL) inactive europium clusters or second phases of europium compounds. The present study investigates the influence of Li-codoping on the radiation hardness of CsBr:Eu2+. It is reported that the integration of Li+ into the CsBr:Eu2+ suppresses the generation of M-centers during x-irradiation and thereby partially improves the radiation hardness.