The problems of distribution of the chemical potential of vacancies in a crystal with a cellular dislocation structure, the evolution of the properties of the lattice and its imperfections in the process of plastic flow, the contribution of diffusion to the motion of lattice dislocations, and their annihilation and transformation into grain boundary dislocations are considered. An analysis of the phenomena that occur inside and in the walls of dislocation cells in the formation of large-angle boundaries shows that intense cold plastic deformation activates the diffusion mass transfer.