Abstract: N-doped activated carbons for electric double-layer capacitors were prepared from waste medium density fiberboard using K₂CO₃ activation. The effects of carbonization temperature, activation temperature, activation time and K₂CO₃/coke mass ratios on surface chemical compositions, pore structure and electrochemical performance of the resulting activated carbons were investigated. Results indicated that the activated carbons had nitrogen contents from 0.93-2.86%, Brunauer-Emmett-Teller specific surface areas from 569m²/g to 1027m²/g and specific capacitances from 147F/g to 223F/g, depending on carbonization and activation conditions. The maximum specific capacitance was attributed to a high surface area, optimum pore size, large pore volume and high N-5 (the pyrrolic nitrogen and pyridinic nitrogen in association with oxygen functionality) content.