Plenty photoluminescence (PL) and plenty photoluminescence excitation (PLE) spectra, as well as layer structure and surface substances on Si crystallites of porous silicon prepared by different technique, have been investigated by photoluminescence, atomic force microscope (AFM) and infrared (IR) transmission methods. It is shown that PLE spectra, consisted of several excitation bands, do not depend on Si crystallites sizes. The nature of excitation bands is discussed.