Nanostructured manganese dioxides (MnO2)/carbon nanofibers (CNFs) composites were fabricated by combining electrospinning technique and hydrothermal treatment. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, cyclic voltammetry and galvanostatic charge/discharge methods were employed to characterize the structure and morphology of MnO2/CNFs composites and to evaluate their electrochemical performance as freestanding electrodes. The results showed that gamma-MnO2 nanocrystals were incorporated into the monolithic CNF substrate and the morphology of gamma-MnO2 evolved from nanoparticles toward nanoneedles with the increase in dipping time. At short dipping time, the gamma-MnO2 nanoparticles were embedded into CNFs and thus showed a specific capacitance as high as 265 F/g and superior rate capability due to their good electrical connection to CNFs. (C) 2011 Elsevier B.V. All rights reserved.