Abstract: High surface area activated carbons were prepared by the KOH activation of coal tar pitch. Two purification methods were used, (i) the pitch was deashed before activation or (ii) the activated carbon was deashed after activation, both with hydrochloric acid and hydrofluoric acid. The effect of the deashing methods on the ash content, morphology, pore structure and electrochemical performance of the carbons for use as supercapacitor electrode materials was investigated. Results indicate that the activated carbon prepared with the pre-deashing treatment has a lower ash content (0.1 wt.%), higher surface area (2722 m² g^-1) and better electrochemical performance than the one produced by the post deashing method. The pre-deashed sample has a specific capacitance of 295 F g^-1 at a current density of 0.2 A g^-1, a good rate capability of 192 F g^-1 at 10 A g^-1 and a capacitance retention rate of 99% after 5000 charge-discharge cycles. A symmetrical supercapacitor using the pre-deashed sample delivers an energy density of 9.1 Wh kg^-1 at a power density of 50 Wh kg^-1.