This work determines on an in vitro porcine urothelium model the threshold values of different parameters such as photosensitizer concentration, irradiation parameters and production of reactive oxygen species in order to control the damage on normal urothelium and spare about 50% of normal mucosa. For a three hours HAL incubation time, these threshold values were with blue light (0.75J/cm at 75 mW/cm² or 0.15J/cm² at 30 mW/cm²) and with white light (0.55J/cm², at 30 mW/cm²). This means that for identical fluence rates, the threshold value for white light irradiation may be 3 times higher than for blue light irradiation.