Amorphous hydrogenated carbon nitride layers, a-C:N:H, were fabricated by radio-frequency, 13.56 MHz, plasma assisted chemical vapor deposition (RF-PACVD) from gaseous CH4 and N-2 diluted in argon. Five series of layers were deposited at various processing conditions. In the respective experiments one of technological parameters (pressure, radio frequency power, temperature, CH4 or N-2 flow) varied while the other were kept on constant level. The optical and structural properties of the layers were studied with use of spectroscopic ellipsometry and Fourier transform infrared spectroscopy (FTIR). It is shown that the layers deposited at various technological conditions, but for the same time duration, have different thicknesses. An influence of the processing parameters on the layers growth rate is discussed. The differences in atomic structure of the layers, as revealed by the FTIR spectra and optical constants (refractive and extinction indices, band gap) are shown to be insignificant.