Wereport the optical and electrical band gap energy of amorphous hydrogenated carbon nitride (a-HCNx) and carbon nitride (a-CNx) as a function of nitrogen concentration (N/C). The optical band gap of a-HCNx and a-CNx films has been determined by means of Ellipsometry and UV-VIS. Both optical and electrical band gaps increase with elevated nitrogen concentration. Experimentally obtained electrical band gap is compared with the same one calculated from single particle band gap or carbon nanotube model to observe the dependence like behavior. Moreover, resistivity of the a-HCNx film shows a higher value in comparison to that of the a-CNx film as the nitrogen concentration increases from 0.07 to .54 at room temperature. (C) 2012 Elsevier B.V. All rights reserved.