Different samples of porous Si have been investigated through Auger electron spectroscopy, The Si LVV lineshape of porous Si is different with respect to that of pure Si and the main peak is shifted to lower kinetic energies. Porous Si is modeled by a first-principle calculation of the electronic states of thin silicon wires (LMTO-ASA method). The main experimental finding is related to the new properties of the valence states in porous Si. The calculated Auger lineshape provides an interpretation of the characteristic shape of the measured spectra. We prove that the confinement shift is not detected by the Si L(2.3)VV Auger signal and that the Si atoms probed are bonded with H and H-2.