By using a “Depthometer with an isotropic fiber-optic probe” developed by the authors, the diffuse reflectance as well as the fluence rate distributions in the normal and cancerous human lung tissues irradiated by a collimated broad beam of a violet Kr⁺laser(406.7～415.4 nm) have been accurately measured. In combination with the diffusion theory and the Adding-Doubling technique, the optical characteristics of human lung tissues, such as the absorption and the reduced scattering coefficients, the penetration depth and the effective attenuation coefficient, were derived. The experimental data agree well with the fitting results by Monte Carlo simulations. It is believed that this original set of data on the optical parameters will be very useful for the lung cancer photodynamic diagnosis (PDD) and the light dosage designations.