A novel method to obtain diffusion-controlled atomic concentration profiles in II–VI semiconductor heterostructures has been developed using high-resolution x-ray diffraction. Measured diffraction spectra are compared with simulations based on direct summation of scattered waves across the heterostructure. In this approach, short-range variations of structural parameters, including the concentrations of the components, interface roughness, etc., can be easily introduced into the simulation routine. The application of the fitting procedure to the experimental spectra taken from variously annealedCdTe/Hg1−xCdxTeheterostructures grown by metal organic chemical vapor deposition, allowed determination of the Hg (or Cd) concentration depth profile as a function of the annealing temperature. As a result, the activation energy and the pre-exponential coefficient for mercury diffusion was found. The diffusion profiles derived from x-ray diffraction spectra were compared with secondary-ions mass spectrometry results, and the advantages of the new method are discussed. ©1997 American Institute of Physics.