Electrodeposition in highly ordered alumina templates is a powerful technique to produce nanowires with a high length-to-width aspect ratio. However, the uniformity of template filling is rather limited and requires accurate adjustment of the deposition parameters. In this work, the growth behavior and formation of caps during copper nanowires deposition are studied. The copper ion concentration in the electrolyte greatly influences the nanowire growth rate and length uniformity. In particular, this results in strong changes in the caps size, their number and distribution. The analysis of current transients reveals a four-stage growth mechanism mainly determined by diffusion. Image analysis of size and distribution of the caps is performed and correlated to the consumed charge during nanowire growth. This gives a direct link to the uniformity of nanowire length and filling rate as proved by Scanning Electron Microscopy. For the investigated system low copper ion concentrations lead to the most homogeneous filled template. (C) 2015 The Electrochemical Society. All rights reserved.