[en] The theory was developed of X-ray diffraction on undirectionally disordered polytype nH(n/2 n/2) structures containing distributed at random single stacking faults. The analytical form of the formula was used and generalized, for intensity of X-rays scattered by the structures with stacking faults, the form of the formula being given by Halloway. Also the method of calculating the coefficients of characteristic equation and of the boundary conditions, given by Prased and Lele was also used and generalized. As a result, for the monocrystalline reflection of the nH(n/2 n/2) structures, the shifts of Δh₃ and the broadening of Δw were explicitly expressed through the coefficients of the characteristic equation. Whereas, the changes in maximal intensity Isub(max) were expressed through the coefficients of the characteristic equation and the boundary conditions. (author)