Various aspects of the physics of the interaction of GaAs surfaces with H2discharges are shown in this paper. Ultraviolet photoemission measurements have been done on (110) cleaved surfaces. Comparison of the core‐level spectra with electronic structure calculations (molecular orbital model) shows that some of the Ga atoms on the hydrogenated surface have two dangling bonds, instead of one on the clean relaxed surface. This indicates that Ga–As bonds on the (110) surface have been broken by exposure to the hydrogen in our discharge conditions. In parallel, some new surface states in the valence‐band region are detected which we have tentatively attributed to the formation of As–H bonds. Onp‐type (110) cleaved surfaces, the Fermi level is pinned near valence‐band maximum (VBM) +0.4 eV after hydrogenation. In a second part of the paper, we describe x‐ray photoemission spectroscopy results on the plasma treatments of GaAs(100) wafers in H2/AsH3(deoxidation, Fermi level position as a function of the surface stoichiometry, etc.).