The paper demonstrates that polymer surface may be modified by means of carbon nitride layers (a C:N:H) formed by Plasma Enhanced Chemical Vapor Deposition method. The layers were deposited from CH4/N2/Ar plasma generated by radio-frequency waves (13.56 MHz) and microwaves (2.45 GHz). A series of experiments enabled determination of technological parameters appropriate to deposit well-adhering and high quality layers on PC, Plexi and PET surfaces. The obtained layers were subjected to structural and chemical composition studies employing energy dispersive X-ray spectroscopy (EDS) and Fourier transform infrared spectroscopy (FT IR) techniques. It was established that roughness parameters of the samples with layers were visibly lower than the parameters characterizing the surfaces after pre-treating with Ar plasma and remained on the same level or were slightly lower than those for raw polymer surfaces.