The paper presents the results of studies of the phenomena of ion transfer in high-temperature modifications of single-crystal copper selenide as a function of temperature and composition within the homogeneity region, as well as the effect of the degree of perfection of single-crystal samples on ion transfer. The activation energy estimated from the temperature dependences of the ionic conductivity for perfect single crystals is significantly higher than in polycrystalline samples and increases with deviation from stoichiometry. Single crystals have lower values of ionic conductivity and chemical diffusion.