An optical element (50), comprising: a substrate (52), an EUV radiation reflecting multilayer system (51) applied to the substrate, and a protective layer system (60) applied to the multilayer system and having at least a first and a second layer (57, 58). The first layer (57) is arranged closer to the multilayer system (51) than is the second layer (58) and serves as a diffusion barrier for hydrogen. This first layer (57) has a lower solubility for hydrogen than does the second layer (58), which serves for absorbing hydrogen. Also disclosed are an optical system for EUV lithography with at least one such optical element, and a method for treating an optical element in order to remove hydrogen incorporated in at least one layer (57, 58, 59) of the protective layer system and/or in at least one layer (53, 54) of the multilayer system (51).