A Eu-doped CsBr-type storage phosphor screen or panel has been disclosed, providing ratios of ultraviolet luminescence intensities of at least 10/9 after having been exposed to radiation having a wavelength in the range from 150 to 400 nm, measured at same sites without and with pretreatment exposure of said storage phosphor screen or panel with short ultraviolet radiation in the range from 150 to 300 nm and having an energy of 10 mJ/mm.sup.2, as well as a method of producing a stimulable phosphor screen or panel, characterized in that during or after at least one of the manufacturing steps a radiation exposure treatment is given with radiation sources emitting short ultraviolet radiation in the range from 150 to 300 nm with an energy of at least 10 mJ/mm.sup.2.