Novel fiber capacitor electrodes presented in this work are produced via a wet spinning technique. The new fiber electrodes consist of polyaniline (PAni)-metal oxide nanocomposite and multi-wall carbon nanotube. Metal oxide nanoparticles such as SnO2, Fe3O4 and TiO2 are incorporated into PAni matrix during in situ chemical oxidative polymerization for improving the capacitance performance of polyaniline. The polyaniline-metal oxide nanocomposites are characterized by X-ray diffraction (XRD). Fourier transform infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM). The electrochemical properties of fibers are investigated by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and galvanostatic charge-discharge techniques in various acidic media. The results of EIS clearly reveal the effects of size and charge of anions on the capacitive response of the fibers. A specific capacitance of 29.7 F cm(-2) based on PAni-SnO2-MWCNT is obtained in 1 M HCl solution compared to 24.1 F cm(-2) for PAni-Fe3O4-MWCNT, 14.2 F cm(-2) for PAni-TiO2-MWCNT, 12.1 F cm(-2) for PAni-MWCNT and 9.8 F cm(-2) for pure PAni fibers. These results make the polyaniline nanocomposite fibers as promising electrode candidates for the supercapacitor applications. (C) 2012 Elsevier Ltd. All rights reserved.