Cuprous and cupric oxides are considered to be the materials of large strategic potential from the viewpoint of their application in photovoltaics. In the present study we have demonstrated the possibility to form photosensitive nanostructured copper oxide layers with extremely large surface roughness by means of chemical and electrochemical oxidation of copper. These nanostructures were characterized using X-ray photoelectron spectroscopy, scanning electron microscopy and photoelectrochemical techniques. An attempt has been made to evaluate the electrochemically active surface area (easa) of CuxO nanostructures on the basis of amount of charge consumed for their reduction, Q. Following values of surface roughness factor f(SR) were obtained: 250 +/- 15% for chemically and 825 +/- 20% for electrochemically formed nanostructured oxide layers. Significantly higher values of Q(c), and, consequently, f(SR) of electrochemically formed nanostructured CuxO layer were ascribed, however, not to larger surface roughness but to the presence of more compact thick oxide layer lying beneath the loosely-packed upper one. Possible mechanism for the growth of nanostructured copper oxide layers has been proposed. It has been demonstrated that electrochemical oxidation allows forming thicker oxide films, which are more photosensitive, compared to chemically formed ones. (C) 2013 Elsevier Ltd. All rights reserved.