X-ray diffraction in multilayer structures is determined by the electronic concentration profile, which depends both on the atomic concentration and on the specific volume. Probing with photons of different wavelengths in the vicinity of an absorption edge (anomalous X-ray scattering) produces a variation of the scattered intensity, which allows the separation of both contributions. A test of the feasibility of this method on several multilayer samples is presented. The technique appears to be sensitive enough to measure specific volume ratios with a precision of about 5%.