Liposomal pharmaceutical formulations incorporating porphyrin photosensitizers useful for photodynamic therapy or diagnosis of malignant cells. The liposomal formulations comprise a porphyrin photosensitizer, particularly the hydro-mono benzoporphyrins (BPD) having light absorption maxima in the range of 670 780 nanometers, a disaccharide or polysaccharide and one or more phospholipids.