The longitudinal photodetectors are widely used in different devices of optoelectronics as the detectors of azimuth shift of the light source, semiconductive layers of the IR-image converters and other position-sensitive devices. The longitudinal type photodetectors considered in the present work are prepared on a base of CdSe:Cu thin layers obtained by the chemical deposition from aqueous solutions. As the first electrode, the In₂O₃ layer was preliminarly deposited onto glass substrates. For activation of samples the CuCl added to solution and annealed in CuCl furnace at temperatures of 350—450 °C for 5—30 min. Investigation of dark and light conductivity, the spectrum and kinetics of photoconductivity of CdSe films have been carried out. The studies of the current-voltage characteristics of In₂O₃-CdSe:Cu have been performed based on the generalized approximate theory of injection contact phenomena in semiconductors. The volume (n₀) and precontact (n_c) change carrier concentration, recombination (N_rec) and trapping (N_cn) center concentration, the absorption adge and the transmission coefficient, the region and minority carriers have been determined. The dark I-U characteristics is sublinear, while the light I-U characteristics is superlinear that causes the stimulation of sensitivity at elevated voltaged. The absorption spectrum and the PC spectrum of the CdSe annealed samples and also of Cu-doped samples, CdSe:Cu have been investigted. The existence of surface condition and the presence phase transition play an dominated role in the formation of optical spectra. The absorption edge for the annealed samples corresponds to cubic modification and in the transmission range a wide diffuse band imposed on the fundamental edge of a single crystalline CdSe is observed. The CdSe:Cu films obtained by chemical deposition method are characrized by high reproducibility, sensitivity in the wavelenght region of l = 0,6 mm, electric strength (10⁶ V/cm), high-resistivity ( r ~ 10⁹—10¹⁰ Ohm·cm), optical transmission (more than 60 %), appearing essential factor for the creation of IR-image converters.