Correlation between the photoluminescence (PL), porosity, crystallite size and chemical bonds in porous silicon (PS) prepared by electrochemical etching of Si with different levels of phosphorus doping has been studied. PL is very strongly related to the chemical bonding and depends on the Si, O and C content which is different for PS prepared on Si substrates with different resistivities. The influence of the doping level of Si on the process of electrochemical etching is discussed.