The thermal motion of Cu+ ions in a quasi-two dimensional copper ion conductor CuCrSe2 is studied in the vicinity of the order-disorder phase transition to superionic phase, basing on a single-crystal and powder X-ray diffraction, specific heat and electrical resistivity measurements. The copper ions gradually migrate with temperature decrease to empty tetrahedral sites reaching occupancy equilibrium in the disordered high-temperature phase at T-s = 365 K. The copper migration between Cu alpha and Cu beta tetrahedral sites occurs through the neighboring, face-sharing octahedral holes. Disorder of Cu+ ions brings perturbations in periodic potential of the crystal lattice providing additional scattering centers for electrons. (C) 2014 Elsevier B.V. All rights reserved.