The surface interactions of OH(X(2)Pi) radicals during SiO2 deposition from 1,3,5,7-tetramethylcyclotetrasiloxane (TMCTS)/oxidant (O-2 or N2O) and dimethyldimethoxysilane (DMDMOS)/oxidant (O-2 or N2O) plasmas have been measured by using the imaging of radicals interacting with surfaces (IRIS) method. The reactivity of OH at the surface of a growing SiO2 film has been determined as a function of the applied rf plasma power (P), the precursor-to-oxidant ratio, and the substrate temperature (T-s). For both Si precursors, the surface reactivity (R) of OH during SiO2 deposition on a 300 K Si substrate is similar to0.60 and is unaffected by changing precursor: oxidant ratio but does increase slightly with P. In contrast, at higher substrate temperatures (T-s > 350 K), R decreases to 0.16 +/- 0.10 for 1:10 TMCTS/O-2 plasma (P = 100 W) and to 0.42 +/- 0.03 for 1:10 DMDMOS/O-2 plasma (P = 100 W). The rotational (OR) and translational (E)T) temperatures of the OH radicals have also been determined. The formation and role of OH in SiO2 deposition are discussed and compared with previous results for TEOS/O-2 plasmas.