Semicarbazones present a wide range of biological activities, and their chemistry and pharmacological application have been extensively investigated. A series of publications report on biological activity of semicarbazones derived from aromatic and unsaturated carbonyl compounds. The biological properties of semicarbazones are often related to metal ion coordination and the metal complex can be more active than the free ligand. This work describes the preparation and structural characterization of two copper(II) complexes, mononuclear [Cu(HL)(H2O)]2(SO4)·5.25H2O (1) and binuclear [Cu2(HL)Cl3(MeOH)1.5(H2O)0.5]·0.5MeOH·0.5H2O (2), where H2L – o-vanillin semicarbazone. Compound 1 was synthesized as a result of CuSO4·5H2O interaction with o-vanillin semicarbazone (H2L) in 1:1 molar ratio in distilled water. Making the reaction with the use of CuCl2·2H2O in 2:1 molar ratio in methanol afforded binuclear complex 2. In 1 the monodeprotonated ligand coordinates to copper ion in tridentate mode through the phenolic and carbonyl oxygen atoms, and azomethine nitrogen atom. One molecule of water, additionally coordinated to each Cu(II) ion, define the square planar geometry of the complex cation. The positive charge of each coordination cations is neutralized by dinegative sulphate anion in external sphere. In the crystal of compound 2, there are actually two complex compounds with the formula [Cu2(HL)Cl3(MeOH)2] and [Cu2(HL)Cl3(MeOH)(H2O)] in a 1: 1 ratio. A molecule of monodeprotonated ligand is coordinated to two atoms of copper(II). The first atom of Cu(II) is bonded through the phenolic, hydrazinic nitrogen atom and carbonyl oxygen atom; the second is coordinated through oxygen atoms of hydroxy- and methoxy- groups. So, the ligand acts as a tridentate [O,N,O] donor to one metal centre and bidentate [O,O] donor to other metal with phenolic oxygen acting as a bridge. Three chlorine ions are coordinated differently: one Cl- serves as bridge between two ions of Cu(II), and other two Cl- ions are coordinated to each of Cu(II). It should be noted that the first metallic centre is five coordinated, while the other – six coordinated, due to the supplementary coordinated molecules of methanol and water. As a result, two coordination geometries are formed: distorted square pyramidal for Cu1 and octahedral for Cu2. e-mail: bourosh.xray@phys.asm.md, ddragancea@gmail.com Molecular structure of [Cu(HL)(H2O)]2(SO4) Molecular structure of [Cu2(HL)Cl3(MeOH)2]