Copper(II) complexes of peptides containing a histidine (His) residue at the third position (known as ATCUN or NTS motif) gain interest for their biological roles and biotechnological applications. We characterized three such peptides, Ala-Ala-His-NH2 (AAH-am), Ala-beta Ala-His-NH2 (ABH-am) and beta Ala-Ala-His-NH2 (BAH-am) by cyclic voltammetry in order to assess the influence of substitution of the alpha-alanine residue (Ala) by beta-alanine (beta Ala) on their redox properties. The obtained results, complementary to the previously reported potentiometric and spectroscopic studies confirmed strong effects of size and position of component chelate rings, 5-membered for Ala and 6-membered for beta Ala, on the Cu(II) binding affinity and redox properties. The detailed voltammetric study revealed the effects of the composition of the supporting electrolyte and the selection of starting potential on the observed redox processes. The conclusions are relevant for designing artificial nucleases and proteases and for proper practice of studies of redox properties of complexes of Cu(II) carried out in buffer solutions. (C) 2017 The Electrochemical Society. All rights reserved.