The effect of Zn(II) concentration on the electrodeposition of zinc oxide on very thin anodic alumina membranes has been investigated. The aim was to establish the best experimental conditions to completely fill the pores to facilitate the further growth of nanorods projected outside the template surface. Zinc perchlorate and molecular oxygen were employed as precursors for zinc oxide formation. Considering local pH changes that take place at the interface, diagrams of species distribution vs pH were built to interpret the steps of zinc oxide formation as the pores are progressively filled. The process was followed, recording the corresponding j/t transients. With the progressive diminution of Zn(II) concentration, the transients evolved from a "metallic type" growth (i.e., similar to that found during the growth of bulk zinc oxide films) toward a stationary state, similar to that reported for the growth of zinc oxide nanorods by self-assemby from solutions with low Zn(II) concentrations. SEM images showed that bundles of zinc oxide nanorods were partially liberated from the template at the lower concentration employed, behavior attributed to a progressive dissolution of the very thin anodic alumina membrane.