Carbon nanotubes (CNTs)-based polyoxometalates (POMs)-functionalized nanocomposites were synthesized by simply functionalizing CNTs with Keggin and Dawson-type POW The positively charged polyelectrolyte poly (diallyldimethylammonium chloride) (PDDA) was introduced to assemble negatively charged POMs and CNTs. The composition, structure and morphology were investigated by UV-visible (UV-vis), Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). Cyclic voltammetry (CV) was employed to investigate the electrochemical properties of the resulting nanocomposites. The cyclic voltammograms indicate that the electrochemical properties of POMs are fully maintained. Functionalizing CNTs with POW not only retains the unique properties of nanotubes, but also endows CNTs with the reversible redox activity of POW. (c) 2006 Elsevier Ltd. All rights reserved.