Treating a reflective optical element (104) for the EUV wavelength range that has a reflective coating on a substrate. The reflective optical element in a holder (106) is irradiated with at least one radiation pulse of a radiation source (102) having a duration of between 1 μs and 1 s. At least one radiation source (102) and the reflective optical element move relative to one another. Preferably, this is carried out directly after applying the reflective coating in a coating chamber (100). Reflective optical elements of this type are suitable in particular for use in EUV lithography or in EUV inspection of masks or wafers, for example.