Porous silicon layers are prepared by laser deposition in different low-pressure ambients. The specimens deposited under vacuum or the O-2 atmosphere have the main photoluminescence in the yellow and those deposited in H-2 have photoluminescence in the red region of wavelengths. The surface morphology and surface conductance of the specimens, investigated by scanning tunnelling microscopy, show gap features with correlation between the PL spectra and the density of electronic states.