AbstractThe dynamical theory of X‐ray diffraction in crystals with randomly distributed small defects based on an optical coherence formalism is used for calculations of integrated reflectivities (in the Laue case) of crystals with statistically placed small precipitates. It is shown that in the case of thinner crystals the integrated reflectivity is influenced mainly by the diffuse scattering, which increases the integrated reflectivity, for thicker crystals a decreasing effect of the diffuse absorption dominates. The calculated thickness dependences of integrated reflectivities are proved experimentally by projection topography of wedge‐shaped crystals with growth striations containing precipita