Activated carbons with high specific surface area (even above 2000 m(2) g(-1)) and pronounced microporosity are prepared in two-stage process involving conventional carbonization of waste hemp fibers and subsequent activation by potassium hydroxide. Samples with considerably different surface and intrinsic micro-and mesoporous properties are obtained at different carbonization and activation conditions. The improvements of the capacitive properties are found upon increase in carbonization temperature, since it considerably influenced the specific surface area and the content of surface oxygen groups. Cyclic voltammetry experiments reveal the dependence of specific capacitance on the sweep rate due to the characteristic porous structure of the samples. The highest measured value in 1 M H2SO4 solution is 122 F g(-1). The electrochemical impedance data indicates eight-branch transmission line equivalent electric behavior of activated carbons. (C) 2017 The Electrochemical Society. All rights reserved.