Our results with the polycyclic (hetero-)aromatic dimers gives valuable insight into the impact of heteroatom substitution on binding energy in these types of systems. We have shown that a significant amount of the variation in binding energy between dimers can be explained by dipole cancellation. This is why dimers of more polar compounds have greater potential for large binding energies, but not all conformers benefit from this extra binding energy -if the dipoles are not opposed, there is no significant dipole cancellation, and thus no significant benefit from the extra polarity. Investigations correlating other observable properties such as total dipole, contact surface area, and distance between heteroatoms did not provide useful insights into binding energy changes. More work is needed to fully understand the factors that determine favourable association between polycyclic heteroaromatic compounds, including those larger than the 3-ring systems considered here, but dipole cancellation clearly plays a large role.