The coatings comprised of the nanodiamond-based and amorphous-carbon-based phases (a-C:ND coatings) are investigated. The a-C:ND coatings were synthesized by chemical vapor deposition in the arc discharge plasma (by plasma chemical deposition) at various concentrations of Ar/H2/CH4. Raman spectroscopy showed that, apart from the diamond substructure, studied coatings contain amorphous-carbon-based and polyene-based phases, while diamond phase is passivated by hydrogen to different degrees. The interplay between the deposition parameters and materials' structure is analysed. It was shown that the ordering of the amorphous substructure and the formation of the phase boundaries affect the electron transport and secondary electron emission properties. The subject of the investigation of the true secondary electron spectra for the analysis of the nanostructured carbon materials is analysed. It was shown that the change of the polyene fraction in the structure of the samples leads to the variation of the ratio of field emission and thermionic emission. The influence of the structure and phase composition of the samples on their electron emission properties is investigated. In particular, their effect on the turn on-field, which value varied in the 9-18 V/μm range for the studied samples, is analysed.