Chemical reversible oxidation of guanine moieties after their previous reduction on a mercury electrode gives under certain conditions rise to voltammetric double peak. The origin of this signal, entwined with many questions, is still unknown. The aim of this work is to indicate the answers of these questions by systematically led voltammetric experiments which evaluate the electrochemical nature of guanine oxidation double peak (GODP) in short oligonucleotides (ONs).