Investigations of the electron structure and phase composition of the surface layers in porous silicon with a developed system of nanopores were made with the use of ultrasoft X-ray spectroscopy and X-ray photoelectron spectroscopy. The samples of porous silicon were obtained on the substrates with p-type conductivity under different modes of electrochemical etching. Porous surface layer represents a system of weakly connected pores oriented mainly perpendicular to the surface of silicon wafer. The mean transverse pore dimension is of similar to 50 nm. Silicon dioxide and sub-oxide were found in porous layer. We assume that these phases cover pores surface thus providing a possibility of the use of the structures as nanoreactors. (C) 2012 Elsevier B.V. All rights reserved.