We present herein activated carbon/carbon nano tube (AC/CNT)) composite electrodes for non-aqueous, high voltage electrical double layer capacitors (EDLC). Mixtures comprising CNT and polymeric species were carbonized and further activated, thus forming matrices with unique hierarchical porous structure, with both micro-and meso-pores. The possible use of these electrodes in high energy density EDLC was studied with non-aqueous solutions based on mixtures of acetonitrile and propylene carbonate and tetra-ethyl ammonium tetra-fluoroborate as the electrolyte. The electrochemical performance of the composite electrodes in these non-aqueous electrolyte solutions is much better than that of electrodes comprising activated carbon without CNT. Capacitance higher than 170 F/g EDL at 2.5 V (118 mAh/g) could be demonstrated at a good rate capability with thick electrodes (>100 microns), during very prolonged cycling. After 10,000 cycles the capacitance fading measured was less than 7%. (C) 2013 The Electrochemical Society.