Layers of silicon nanowires with diameters of 20−200 nm, grown by metal-assisted chemical etching of monocrystalline silicon substrates of p-type conductivity with a resistivity of 1−20Ohm · cm and surface orientation (100), which were supplied by three manufacturing companies and were characterized by different lifetimes of photoexcited charge carriers, were investigated by means of the reflection spectroscopy, Raman scattering and photoluminescence. It was found that the Raman intensity for nanowires with length larger than 1micron is 3−5 times stronger than that for the substrates. The intensity of interband photoluminescence at wavelength of 1.12 μm for the nanowires exceeded significantly those of the substrates and it was maximal for the samples with the longer volume lifetime that indicates a low rate of the non-radiative recombination on the surface of nanowires.