The diffraction pattern simulation of four YBa₂Cu₃O_x single crystals with inhomogeneous distribution was successfully carried out on the base of the theory of X‐ray diffraction by disordered interstratified structures. The specific feature of their two‐component irregular mixed‐layered structures is the total segregation of layers with various oxygen content that led to the formation of so‐called intergrowth structures. The concentration of admixture layers varied from 10 to 40% while oxygen content difference within the crystal ranged from 0.5 to 0.3. In one of the crystals the fluctutations of layer heights corresponded to oxygen variation from 6.2 to 7.0.