A theory concerning the coherent X ray radiation of relativistic electrons crossing an artificial periodic medium in Laue scattering geometry has been constructed. Expressions describing the spectral angular characteristics of radiation in the Bragg scattering direction have been obtained and studied. Radia tion is considered in analogy with that in the crystal medium as a result of the coherent summation of the con tributions of two radiation mechanisms, in particular, parametric X ray radiation (PXR) and diffracted tran sition radiation (DTR). It is shown that the DTR yield from a layered target can exceed the particle radiation yield in a single crystal radiator by one order or more under similar conditions.