Two different MnO2polymorphs, namely akhtenskite (ε-form) and nsutite (g-form) were obtained fromthe comproportionation reaction between Mn2þand MnO4. The conditions that administer the trans-formation between both phases i.e. temperature, reflux time and concentration of reactants wereexplored. Other manganese oxide/hydroxide phases are obtained depending on variation of the pH of themedium or the solvent used in the reaction. Heat-treatment of both MnO2polymorphs was done underisothermal and non-isothermal conditions, various pathways were adopted in both cases. The results ofTGA/DTA analysis showed also thatg-MnO2is more stable thanε- MnO2and thatε-form contains muchmore excess mass over its surface (i.e. surface bound hydroxyl groups) thang-form. Surface area mea-surements revealed that the reaction temperature has pronounced effect not only on the product phasebut also on its surface properties. Very high surface area of 345 cm2/g was adopted byε-MnO2anddecreases with increasing of reaction time (239 m2/g). SEM investigations showed thatg-MnO2has aplate-like shape whilstε-MnO2exhibits a sponge-like morphology. Magnetic properties of both oxideswere explored using SQUID magnetometer under zerofield cooled andfield cooled conditions. Bothphases showed a ferromagnetic spin ordering with Curie temperature as 45 K forg-form and 20 K forε-form. The coercive force was found as 2500 and 2130 Oe, respectively. Remanent magnetization was 35and 30 emu mol1forg- andε-MnO2, respectively.