Dissolution mechanism of cubic Pt nanoparticles has been studied with the use of atomic force microscopy on a carbon substrate in 0.1 M NaClO4. The shape of the nanoparticles does not change in the double layer region. The height of the nanoparticles increases slightly at the onset potential of the oxide film formation. The nanoparticles are dissolved from the sides in the oxide film formation region, whereas the change of the height is negligible. These results differ from those of the cubic Pt nanoparticles on a Pt substrate, on which the dissolution proceeds at the upper terrace. (C) 2011 Elsevier B.V. All rights reserved.