The electronic structure of C films deposited by sputtering a graphite target in rf. Ar–H 2 plasma is investigated by photoemission, Auger emission and electron energy loss spectroscopy (EELS) as a function of the H 2 concentration in the feed gas, referred to as [H 2 ]. Adding hydrogen to the plasma causes the films to change from a graphite-like unhydrogenated structure to a non-graphitic hydrogenated structure. The film mass density, as derived from the π+σ plasmon energy, decreases upon H 2 addition to the gas mixture, goes through a minimum at low [H 2 ] and increases with increasing [H 2 ]. It reveals a non-monotonous behavior of the film H content as a function of [H 2 ], the maximum H incorporation occurring at low [H 2 ]. This appears to be a characteristic of C deposition via graphite sputtering in Ar–H 2 plasma and it is discussed in connection with previous results on the subject.