This work addresses the issue of radiation chemical synthesis of MnO2 nanoparticles and also illustrates the ease of formation of nanorods and sheets by adroit manipulation of experimental conditions. The radiation chemical yield (G-value) for reduction of Mn (VII) by the hydrated electron was found to be 0.27μmolJ−1 and 0.17μmolJ−1 respectively, when tert. butanol and isopropanol were used as scavengers in nitrogen-saturated solutions. The colloids formed upon irradiation of air-saturated solution and N2-purged solution with tert. butanol as scavenger were found to be most stable. Irradiation of air-saturated solution containing 4×10−4 MKMnO4 at a dose of 1692Gy resulted in the formation of nanorods of the dimension 100–150nm and nanospheres in the range 10–20nm. Irradiation of N2-purged solution containing tert. butanol as scavenger for OH-produced reticulated structure of nanorods with length varying from 50 to 100nm at a dose of 1692Gy. Elemental analysis was performed using scanning electron microscope on MnO2 formed by reduction and oxidation and the purity was found to be 98% of elemental Mn content.