The results of this Letter reveals that the [Re 3 (μ-Cl) 3 Cl 9 ] 3− , [Re 3 (μ-Br) 3 Br 9 ] 3− , [Re 3 (μ-I) 3 I 9 ] 3− clusters exhibit aromaticity and that spin–orbit effect decreases the aromaticity due to the fact that the 5d 3/2 spinors are more contracted than the scalar 5d orbitals. The [Re 3 (μ-I) 3 I 9 ] 3− and [Re 3 (μ-Br) 3 Br 9 ] 3− clusters are the most aromatic clusters. This can be explained by the np 1/2 and np 3/2 spinors radial expectation (〈r〉) values which follows the Cl<Br<I sequence. Thus, the most extended spinors correspond to I and Br ligands, as indicated in the ELF plots. Furthermore we carried out TDDFT calculations which agrees with the fact that [Re 3 (μ-I) 3 I 9 ] 3− should show the highest value of aromaticity.