The unique properties of the hexaiodobenzene dication are analyzed by the means of density functional theory and compared to those of the analogous hexachloro compound. [C6I6](2+) is fulfilling the Mlckel (4n + 2) rule for both its pi and sigma electrons, so that two orthogonal channels are opened for electron delocalization. This molecule has been chosen as the simplest prototype to set up a computational protocol to study and quantify delocalization at the periphery of a benzene core. We demonstrate that electron delocalization can be quantified by analyzing the variation of both magnetic shielding tensors and of nucleus independent chemical shift. (c) 2006 Elsevier B.V. All rights reserved.