The Girard T reagent and its condensation products with aldehydes – hydrazones, have been intensively used as ligand in coordination chemistry only a few years ago. A series of new complexes with this type of ligands was described by us recently [1, 2]. The coordination compounds of salicylaldehyde or 2-formylpyridine Girard T hydrazones with iron(III) are mononuclear. In this presentation we describe new coordination compounds of salicylaldehyde Girard T hydrazone with copper(II) ions. The formation of mono- or polynuclear systems with this type of ligands is directly depending of the nature of copper(II) salts, substituent, and the solvent that was used. The X-ray investigation shows a monomeric structure in the case of copper(II) chloride, and binuclear structure - for nitrate salt, when as ligand is used the unsubstituted hydrazone. For the 5- methyl derivative the formation of a polynuclear heterovalent copper(II) and copper(I) was observed. The mononuclear units are associated in dimers via phenolic groups. The dimers are assembled in polymer chains by the molecules of Cu(I) chloride present in the structure (Fig.1). The crystal engineering of the complexes, role of the hydrogen bonds in stabilization of the crystal structure is discussed. Studies of the magnetic susceptibility versus temperature show a strong antiferromagnetic interaction between Cu(II) S=1/2 in the binuclear units. For the mononuclear compounds any magnetic interaction between paramagnetic centers has been not observed. Using different substituents in salicylaldehyde moiety it is possible to influence on the value of Cu- 2O-Cu angle and, of course, on the exchange parameter of magnetic interaction J.