Single wall carbon nanotubes (SWNTs) filled and doped with chromium oxide have been used as attractive electrodes for supercapacitors. Pseudocapacitance effects related to the presence of nanosized chromium oxide finely dispersed at the nanoscale together with high conducting properties of SWNTs allow building efficient electrodes from this hybrid material. Even if capacitance values are not very high (ca. 60 F g(-1)), however, extremely quick charge propagation was observed, doubtless due to the overall physical and textural properties of SWNT material. The positive effect - with respect to empty-SWNTs - brought by the presence of chromium oxide in and probably in-between the SWNTs indicates that chromium oxide is accessible to the electrolyte in spite of its encapsulated location, because of the numerous side entries created all along the SWNT walls during the filling step. (c) 2006 Elsevier B.V. All rights reserved.