The effect of boron diffusion on the microhardness and photoluminescent properties of porous silicon layers obtained conventionally by anode etching is studied. By means of angle lap, it was found that the samples have a three-layer structure : the upper layer is a transparent film, the middle-actually porous silicon, and the lower layer is a single-crystal substrate. It is established that boron diffusion into the cathode surface increases the luminescence intensity, while diffusion into the anode surface decreases it, and the thickness of both the porous and surface silicon compound layers increased in both casts. A conclusion is drawn that the gradient or internal stresses in the substrate produces a positive effect oil the luminescence intensity of the porous layer grown on it. A luminescence model allowing for both the role of silicon compounds and the quantum-sits hypothesis is proposed.