We have investigated the capacitance of an electric double layer capacitor (EDLC) composed of poly(vinylidenechloride) (PVDC)-derived carbon electrodes as a function of precursor crystallite size. The crystallite size of the precursor strongly affects the crystallinity and the pore structure of carbon when heat-treated at 700 degreesC, and this might be due to different carbonization behaviors, resulting in a variation of the capacitance in the EDLC. The highest capacitance (90.54 F/g, which is equivalent to 362.16 F/g for a conventional three-compartment cell) is obtained when PVDC with a crystallite size of 330 Angstromderived carbon is used for the electrodes in the EDLC. This suggests that the pristine polymer crystallite size may be considered as an important tailor-made factor that can be used to affect the final structure. (C) 2002 The Electrochemical Society.