The presence of weak intramolecular interactions among the axial carbon atoms in Ru-3(CO)(12), previously detected by topological analysis of the 120 K X-ray derived charge density, has been here confirmed by theoretical calculations on the isolated, "gas-phase" molecule, using the all-electron B97D/3-21G approach, as well as by further experimental determinations of higher accuracy on data collected at 100 K. The importance of using density functional theory (DFT) approaches where dispersion terms are explicitly added to the usual Kohn-Sham energy to reproduce such weak intramolecular interactions has been evidenced. This result confirms the multipole approach as an efficient and sensitive tool to extract fine details of electron density distributions.