This invention relates to dry pharmaceutical compositions comprising an active ingredient which is 5-aminolevulinic acid (5-ALA) or a precursor or derivative of 5-ALA, or a pharmaceutically acceptable salt thereof. The compositions may be used in the photodynamic treatment (PDT) or photodynamic diagnosis (PDD) of cancer, pre-cancerous conditions and non-cancerous conditions. The invention relates further to irradiation devices comprising dry compositions and the use of such devices in the photodynamic treatment (PDT) or photodynamic diagnosis (PDD) of cancer, pre-cancerous conditions and non-cancerous conditions.