Initiated CVD (iCVD), a dry method, is able to produce poly(methyl methacrylate) (PMMA) thin films by utilizing a reactive gaseous mixture of the monomer methyl methacrylate and the initiator triethylamine. The deposition rate is twenty times faster with the use of the initiator. Fourier-transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) show high structural resemblance between iCVD PMMA and conventional PMMA, and the degree of functionality retention increases with decreasing residence time in the vacuum chamber. XPS detection of nitrogen incorporation is consistent with the incorporation of the initiator into the polymer chains. NMR spectroscopy on completely dissolved films shows that the tacticity of iCVD PMMA resembles that of conventional, radically polymerized PMMA. Altogether these observations support the hypothesis that, for iCVD PMMA, the polymerization is by a free-radical mechanism.