A poly(1,5-diaminoanthraquinone) [poly(DAAQ)], which is a conducting polymer condensed with 1,4-benzoquinone, was studied electrochemically and was proposed as a new category of electrochemical capacitor material. In common nonaqueous media, the poly(DAAQ) showed two sets of reproducible redox couples for repeated cycles. The potential window of the material was in the range from cn. -1.5 to +1.0 V (vs. Ag/AgCl). hz situ UV-visible spectroscopy suggested that the redox couple observed around -1.5 V is responsible for the quinone group and that around +1.0 V is due to the pi-conjugated system. The poly(DAAQ) showed high conductivity (0.3-2.0 Ohm(-1) cm(-1)) over a wide range of potential (-2.0 to 0.8 V), which suggests extension of the pi-conjugated system. It is proposed here that one can construct an electrochemical capacitor device by utilizing poly(DAAQ) as both positive and negative electrodes. We constructed the poly(DAAQ)/poly(DAAQ) electrochemical capacitor for test purposes. The poly(DAAQ)/poly(DAAQ) electrochemical capacitor exhibited high specific energy (25-46 Wh kg(-1)) and high specific power (10,200-30,500 W kg(-1)) at discharge rates from 30 to 90 C.