The influence of the position of the counter electrode on the behaviour of a cylindrical electrochemical reactor with a three-dimensional electrode in flow-by configuration is analysed. Experimental results of the potential distribution are compared with theoretical predictions obtaining a close agreement between them. The best performancewas observed for the arrangement with an outer counter electrode, where the largest bed thickness is obtained for a given potential difference in the three-dimensional structure; which, under limiting current conditions, tolerates a higher current increasing the conversion per pass. The reactor was also checked for the removal of copper from dilute solutions and the experimental results coincide with the theoretical predictions. The morphology of the electrodeposited copper is discussed as a function of the radial position inside the three-dimensional structure. (C) 2014 Elsevier Ltd. All rights reserved.