This work reports on the main competing processes and their contribution to the properties of SiO2 layers on polymers in large area AP-PE-CVD from Ar-N2-O2-HMDSO mixtures. The detailed space resolved surface analysis on the statically deposited films showed smooth SiOx films in the vicinity of the gas injection, as deposited by HMDSO radicals. At the gas effluent, due to HMDSO depletion, non-depositing species interact with the polymer and induce rough deposits with high carbon content. The competition of plasma-polymer surface interaction with HMDSO radicals deposition, is further confirmed from the analysis of films grown on polymers with a "protecting" layer and with reverse gas flow direction. Under web roll conditions, HMDSO radicals deposition is dominant, resulting in high quality SiOx layers along the whole electrode length. © 2009 WILEY-VCH Verlag GmbH & Co. KGaA.