The experimental results of electrical conduction, optical absorption, steady-state and transient characteristics of photoconductivity in bulk and amorphous thermally deposited chalcogenlde As₂Se₃:Sn and AsSe:Sn thin films are presented. The tin impurity introduced during thermal synthesis of the starting material As₂Se₃ and AsSe has larger effect on transient rather than on steady-state characteristics of photoconductivity. The charge carrier transport characteristics in these materials are described in the frame of the multiple-trapping model, widely accepted for the amorphous semiconductors. The effect of tin impurity on both extended and localized electronic states are revealed. The tin impurities are also responsible for the photostructural changes of optical properties in AsSe-doped thin films.