Paramagnetic centers were studied in different SiOx:N,H films deposited by plasma-enhanced chemical vapor deposition in a wide composition range. The total dangling-bond concentration is detected to be proportional to the oxygen content. Moreover, sample irradiation by ultraviolet light revealed also that nitrogen impurities play some role. In particular, the presence of N-H bonds induces a release of the him stress, which seems to be related to the concentration of dangling bonds. It is also shown that both weak Si-Si and Si-H bonds may serve as precursors for the dangling-bond formation.