The use of electronically conducting polymers (ECPs) as pseudocapacitive electrode materials in high-power supercapacitors is a challenge to overcome the performance of carbon-based double-layer supercapacitors for applications requiring high power levels. ECPs provide different supercapacitor configurations but devices with the polymer n-doped form as the negative electrode and the p-doped form as the positive one are the most promising in term of energy and power. This type of supercapacitor has indeed a high operating voltage, it is able to deliver all the doping charge and it has in the charged state both electrodes in the conducting (p- and n-doped) states. Data for poly(3-methylthiophene) positive and negative electrodes, envisioned for a n/p-type supercapacitor, as well as data for cyclability of supercapacitors with composite electrodes based on such conventional polymer are here reported and discussed. The capacitance and cycling stability of poly(3-methylthiophene) are sufficiently high to take this polymer into consideration for supercapacitor technology.