The X-ray plane-wave diffraction scheme was used for experimental testing of biological objects—blood vessels and laboratory animals. Two successively installed asymmetrically cut monochromators were used for the pseudoplane-wave preparation. The images were formed by analyzer fixed both in Laue and Bragg positions. Possibility of vessel system observation both in a live organism and cadavers was demonstrated in a number of experiments. The method has proved to be very promising in the non-invasive X-ray diagnostics.