Hydrogen is found to influence the porous Si/PSi system. H atoms cannot be detected by AES or XPS, but profound effects have been observed on PSi using the elastic peak electron spectroscopy (EPES) in the 50–100 eV range after HF treatment of PSi samples. Limited numbers of low energy cross sections are available in the literature. The data of Joy et al are confined to 20 and 50 eV. The differential cross sections of electrons have been calculated in the present work in the 2–50 eV range for H, Si and O, i.e. elements composing the surface of PSi. The relativistic and nonrelativistic PWEM method was used in calculations. The electron-atom interaction was described by the TFD potential, using a recent approximation, in view of considerable errors of earlier approximations. Some experimental data are available for gaseous hydrogen. They turn out to be in good agreement with our calculated values. The total elastic, scattering, the total backscattering and the backscattering cross sections integrated within the angular range (124–176 °) of RFA, σ RFA, have been calculated for monolayer of H, Si and O. They strongly increase with decreasing energy. In the case of Si, a broad maximum is observed and strong decrease below 20 eV, with a deep minimum between 2 and 10 eV. Here σ RFA,H ⪢ σ RFA,Si, EPES is promising in this very low energy range for the system H/Si, analogous to H/W.