To investigate the relationship between pore structure and specific capacitance of electric double layer capacitors with non-aqueous electrolytes, phenol resin based carbon spheres were modified by oxidation in dry air, giving a wide range of pore structure. Surface area due to the presence of different pores was characterized through α s plots of adsorption isotherms of N2 gas at 77K as microporous surface area (S micro.) due to micropores and external surface area (S ext.) mainly due to the mesopores. A simple model can be presented by recognizing the different contributions of S micro. and S ext. in forming electric-double layers. The capacitance per unit external surface area was larger by one order of magnitude than that per unit surface area of micropores (0.187F/m2 versus 0.017F/m2 at charge–discharge current of 4mA/g), revealing greater contribution of external surface to specific capacitance for electric-double layers than surface of micropores. With the increase in charge–discharge current to 40mA/g, the relative contribution of external surface became more significant, which was supposed to be due to large sizes of electrolyte ions, Et3MeN+ and BF4 −.