Si wafers (CZ, boron doped, 3–20 Ohm cm) with (100) or (111) oriented surfaces were treated in aqueous HF (0.2%, 1%, 5%, 40%) and measured with X‐Ray Photoelectron Spectroscopy (XPS) and High Resolution Electron Energy Loss Spectroscopy (HREELS). The HREELS spectra exhibit vibrational excitations characteristic of a predominant coverage with Si‐dihydride on Si (100) and with Si‐monohydride on Si (111). After treatment in diluted HF additional OH groups could be observed. The coverage with fluorine is shown to be dependent on the HF concentration and amounts to roughly 1–1.5⋅101 4 F/cm2 or 10% of a monolayer after a 40% HF dip. Some hydrocarbon and spurious oxygen contamination could be observed, too. Water rinsing after the HF dip lowered the fluorine coverage via a substitution reaction Si‐F+H2O→Si‐OH+HF, as OH groups were detected afterwards. Prolonged water exposure led to the development of a hydrous oxide on part of the surface. A mechanism for the preferential attachment of H to the Si surface is discussed, which is based on the polarization of the Si‐SiX bonds by electronegative groups on the surface.