Structural and electronic properties of electrodeposited Cu(OH)(2) films on Au electrodes in alkaline solutions have been characterized in situ by Co K-edge X-ray absorption spectroscopy (XAS). The results obtained have shown that freshly prepared films undergo spontaneous partial and irreversible oxidation in 1 M KOH solution even when polarized at -0.58 V vs. Hg/HgO,OH-, as evidenced by the presence of contributions (ca. 20%) from Co-O and Co-Co shells in the extended X-ray absorption fine structure (EXAFS) attributed to CoOOH. Subsequent polarization of the electrode at + 0.6 V oxidizes a significant fraction, but not all of the Co(OH)(2) into CoOOH, as judged by the occurrence of Co-O and Co-Co shells in the EXAFS ascribed to Co(OH)(2). Further reduction of the same film at -0.58 V vs. Hg/HgO,OH- increased the amount of Co(OH)(2) from 28 to 43%, indicating that the fraction of electrochemically active sites does not exceed ca. 15%. On this basis, the redox activity of Co hydroxide is probably associated with surface rather than bulk Co2+/Co3+ sites in the lattice. These results suggest that Co(OH)(2) present as a distinct pure phase in technical Ni oxide electrodes does not contribute significantly to charge storage during cycling, nor to changes in the redox properties of the electrochemically active material.