Under the influence of previous experimental results, a new theoretical study of current-time relationship in differential pulse polarography was performed. In a reversible electrode reaction, complicated by the reactant adsorption on the static mercury drop electrode, the enhancement of the main peak with increasing drop life-time appears. The effect is explained by the change of reactant concentration at the electrode surface during the drop-life time. Non-Cottrell behavior becomes obvious if, in addition to the net response, its components are analyzed too. (C) 2008 Elsevier B.V. All rights reserved.