The isothermal calorimetry, pH-potentiometric titration and H-1 and C-13 NMR methods has been used to study the mixed-ligand complex formation in the systems Zn2+-Nta(3-)-L- (L = His, Orn, Lys, GlyGly, AlaAla) in aqueous solution at 298.15K and the ionic strength of I=0.5 (KNO3). The thermodynamic parameters of formation of the mixed complexes have been determined. The relationship between the probable coordination modes of the complexone and amino acid or dipeptide molecules in the mixed-ligand complex and the thermodynamic parameters has been discussed. (C) 2014 Elsevier B.V. All rights reserved.