The incorporation and depth distribution of hydrogen, after annealings in low pressure water vapor of SiO2 films thermally grown in O-2 on SiC and on Si, are determined using nuclear reaction analyses. Water isotopically enriched simultaneously in deuterium (H-2 or D) and in O-18 was used. While in SiO2/SiC, the amount of incorporated hydrogen increases continuously with temperature and with initial oxide thickness; in SiO2/Si, there is no such dependence. In SiO2/SiC, hydrogen profiling reveals its presence in the surface, bulk, and interface regions, whereas in SiO2/Si, hydrogen is observed only in near-surface regions of the oxide film. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3477941] All rights reserved.