The theoretical investigation of tetramethylammonium (TMA)-imidazole and TMA-furan complexes has been performed to justify the preferred structure of the cation-aromatic complexes predicated by the analysis of molecular electrostatic potential (MEP) maps of isolated aromatic systems. Such maps have been shown to be helpful in predicting the cation binding sites in cation-aromatic complexes. Our computational results show that a large part of the binding energies in the systems studied are contributed by the classical cation-pi interaction. However, the optimized structure obtained in the MP2 method might be different from that obtained by the DFT method due to the influence of dispersion forces. Dispersion forces have been found to be important in the systems studied, increasing the binding energies by similar to7% and 20% for the TMA-imidazole and TMA-furan systems, respectively.