Abstract: Cypress charcoals, which were prepared under superheated steam and had a relatively large amount of mesopores, were used in electric double layer capacitors (EDLCs) in 1mol/L H2SO4 electrolyte. The gravimetric capacitance of cypress charcoals was about 190F/g at a current density of 50mA/g (C50) and 140F/g at 1000mA/g (C1000) and the performance rating defined by C1000/C50 was about 0.72. The capacitance observed was explained by the contributions from the surfaces from the micropores and the larger pores. By loading minute NiO particles through a simple impregnating process, the capacitance of the loaded charcoals was enhanced by about 13% in gravimetric capacitance and by about 27% in volumetric capacitance and the performance rating was kept the same.