In this work, activated carbons (ACs) with high porosity are synthesized from polystyrene-based ion exchange resin (PIR) by potassium hydroxide (KOH) chemical activation, and the influence of the KOH-to-PIR ratio on the porosity of the ACs and electrochemical characteristics is investigated. As a result, PIR is successfully converted into ACs with well-developed micro and mesopores. The specific surface areas and pore volumes are increased with an increase in the KOH-to-PIR ratio. Furthermore, it is found that increasing the amount of KOH led to a transformation of the micropores into meso-and macropores. The electrochemical performance of the PIR-based ACs is enhanced by high specific surface area and oxygen functional groups. In the application to electric double-layer capacitors (EDLCs), the PIR-based AC with a KOH-to-PIR ratio of 4 (PIR-4) has the highest specific capacitance (258 F g(-1)) and shows excellent electrochemical stability. Thus, it is thought that the PIR-based ACs are suitable electrode materials for EDLCs. (C) 2012 Elsevier B. V. All rights reserved.