Nickel and cobalt mixed oxides [denoted as (Ni + Co) Ox] were electrochemically deposited onto carbon nanotube (CNT) film substrate with a three-dimensional nanoporous structure in aqueous solutions containing different ratios of cobalt(II) and nickel(II). For comparison, the (Ni + Co)O-x were also prepared on nickel mesh substrate. Microstructures and performances of these (Ni + Co)O-x-based electrodes examined by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy showed that (Ni + Co)O-x layers were anodically deposited on the surface of the CNTs. The electrochemical properties of these composite electrodes were investigated by cyclic voltammetry and charge/discharge. The results indicated that the deposition of (Ni + Co)O-x on the CNT film improved the electrochemical performance due to the electrode construction comprising thin electroactive film on the conductive CNT film with a three-dimensional nanoporous structure. Furthermore, the effect of the ratios of Ni/Co on the electrochemical properties of (Ni + Co)O-x/CNT film electrode were also discussed in detail. (c) 2006 The Electrochemical Society.