Carbon nitride (CNx) films were prepared on silicon (100) wafers and ITO conductive glasses by cathode electrodeposition, using dicyandiamide (C2H4N4) in acetone as precursors. The composition ratios (N/C) were approximated to or larger than 1 from XPS. The optical properties and electrical resistivities of the films were investigated. Intense PL with two bands in the range 2.5-3.5 eV was observed on the CNx films. The band gaps (E-opt) deduced from measurements of the optical absorption coefficients in the UV-VIS spectra were found to be in the range of 1.1-1.6 eV. From the PL and UV-VIS spectra, the nitrogen content has a large effect on the PL band gap and E-opt. The electrical resistivities of the films on Si wafers are in the 10(9)-10(10) Omega . cm range. (C) 2003 Kluwer Academic Publishers.