Studies performed on isobutonium cations at the ab initio level show that five different stable structures can be characterized. The two structures most energetically favored correspond to van der Waals complexes, one of them between CH4 and i-C3H7+ and one of smaller energy between H-2 and the C4H9+ cation. Among the isobutonium cations, the most stable structure corresponds to the C-isobutonium cation where a three-center two-electron bond is formed. The isobutonium cations on the H are significantly higher in energy. The topology of the electronic density charge of the isobutonium cations is studied, at ab initio level, using the theory of atoms in molecules (AIM) developed by Bader. The electronic delocalization that operates through the sigma bonds in saturated molecules and specifically in protonated alkanes can be studied by means of the analysis of the charge density and of the Laplacian of the electronic charge density at the bond critical points.