Plasma-polymerized vinyldimethylethoxysilane (PP VDMES) and plasma-copolymerized styrene-vinyldimethylethoxysilane (PC St-VDMES) thin films were prepared in a tubular reactor capacitively coupled to an r.f. power supply. The surface polymer structure as determined by X-ray photoelectron spectroscopy was correlated with the controllable discharge parameters of power, pressure and feed gas composition. PP VDMES films show carbon enrichment and concomitant loss of the ethoxy group (via cleavage of the C-O bond) as the power per molecule ratio P/M is increased during the deposition reaction. The rate of deposition of PP VDMES was also found to be a strong function of P/M. The PC St-VDMES surface chemical structure and deposition rate are complicated functions of the feed gas composition (styrene and VDMES). In both systems it is found that the chemical functionalities of the monomers (ethoxy group for VDMES and phenyl ring for styrene) are retained and incorporated into the plasma-deposited films under low P/M discharge conditions.