It was investigated the ability of biologically active compounds of copper (II) with racemic serine Cu(DL-Ser) to crystallize in polymorphic modifications. The analysis of the earlier obtained structural data by electron diffraction method shows that the crystals of this compound are built from individual centrosymmetric complexes Cu(D-Ser)(L-Ser) related to each other in identical layers. Hydroxyl groups of serine residues of the complexes are concentrated in the interlayer space and form hydrogen bonds between them, and each hydroxyl group of one layer interacts with two hydroxyl groups of rhe neighboring layer, thus forming an infinite chain of hydrogen bonds. It was proved, that the layers in the structure can be combined in 16 various ways of mutual arrangement, without violating the rules of their crystallochemical neighbouring. Obtained in such a way, the structures are possible polytypic modifications of the crystals Cu(D-Ser)(L-Ser). They are built from one and the same structural unit (layer) and differ only by the ways of packing of that structural unit in the crystal space. The crystals of 16 possible structures belong to monoclinic and orthorhombic crystal systems and their structures are the same in pairs. The obtained results permit to predict possible, but not yet detected compounds with new useful properties.