A study was made of the electron paramagnetic resonance (EPR), the Mn3+/Mn4+ ratio, the OH− groups contents, the ionic conductivity value and the specific capacity in different electrolytically and chemically prepared manganese dioxides which were intended for use in power sources. Typical EPR signal for the powdered MnO2 samples is wide single line with g=1.94. The replacement of some Mn4+ ions by Mn3+ modified the character of the exchange interaction. A correlation was established between the width of the EPR signal and electrochemical parameters of the samples. It is supposed that the EPR data can be useful for the semi-quantitative expression of chemical and electrochemical activity of different MnO2 samples.