An influence of complexation of reactant and intermediate on square-wave voltammograms of reversible, two-step electrode reaction is analyzed theoretically. The potentials of the first and the second peak of the split net response depend on stability constants of complexes, the standard potentials of individual electron transfers and on the concentration of ligand: E-p.1 - E-0(1) = (RT/F)(In F-M + In FM2+) and E-P.2 - E-1(0) = E-2(0) - E-1(0) - (RT/ F) In FM+, where FM2+ = 1 + beta C-1.a(L) - beta C-2.a(L-)2 + ... and FM+ = 1 + beta C-1.b(L)- + beta 2.bCL-(2) + ... (C) 2012 Elsevier Ltd. All rights reserved.