The molecular electrostatic potential (MESP) and polarization-corrected MESP (PMESP) minima for some small molecules are calculated on the surface generated by rolling cations (Li+ and Na+) on their van der Waals surfaces. The cation binding energies of these molecules are obtained with HF/6-31G** level ab initio calculations. A noteworthy outcome of the present study is that the plot of these binding energies and the corresponding PMESP surface minimum values turns out to be remarkably linear with a slope close to unity. The PMESP is thus found to work as a powerful tool for unearthing the patterns of cation binding sites and energetics for molecular systems.