A method has been disclosed for manufacturing a storage phosphor for use in a photostimulable phosphor screen or panel comprising a support and a storage phosphor layer, wherein a dopant or activator is incorporated more homogeneously in amorphous and in crystalline phosphors as well, starting with a mixing step of said matrix component and activator component in stoechiometric ratios in order to provide a desired phosphor composition; and more particularly in order to prepare a CsBr:Eu.sup.2+ phosphor having an optimized sensitivity with respect to its particle size.