This study examined the dispersion behavior of graphene oxide (GO) and oxidized carbon nanotubes (o-CNT) in a polar solvent, as well as the differences in the behavior related to the Hansen solubility parameter windows. In polar aprotic solvents, GO and o-CNT showed similar dispersion behavior. On the other hand, in polar protic solvents, such as ethanol and isopropanol, GO did not show dispersion stability whereas the o-CNTs did. This difference in the dispersion behavior between GO and o-CNTs resulted from the stronger hydrogen bonding between the GO interlayer induced by a large amount of oxygen functional groups and flexible two-dimensional morphology with a large surface area. (C) 2011 Elsevier B. V. All rights reserved.