Manganese oxide (MnO2) powders with various nano structures were prepared using MnSO4 as a precursor through hydrothermal method. Manganese oxides with needles, rods and flakes structure were formed depending on oxidizer used. The flakes-shaped MnO2 exhibited the higher capacitance values than other structures, both in aqueous and organic electrolytes. The charge storage mechanism observed in aqueous electrolyte is mixed type of charge insertion-extraction and surface adsorption mechanism while that in organic electrolyte is insertion-extraction. The higher specific capacitance of 342 Fg(-1) in NaOH, 429 Fg(-1) in LiClO4 and 455 Fg(-1) in LiPF6 was observed for the flakes-shaped MnO2 electrode. (C) 2012 Elsevier Ltd. All rights reserved.