Regularities in the formation of diffraction imaging of dislocations are studied by numerical modeling and experimental section X-ray topography. The study of X-ray scattering by irregularities of the crystal lattice is of interest for several reasons. First, the contrast of defects is connected with the fundamental problem of development of a dynamic theory of X-ray scattering in real crystals. Second, knowledge of the special features of diffraction makes possible a qualitative and, in some cases, quantitative analysis of the X-ray diffraction contrast of defects in a crystal lattice (measurements of the deformation, determination of the sign and parameters of the Burgers vector, etc.).