Here, we report density functional calculations of the electronic structure and nuclear independent chemical shift (NICS) values of the Re3Cl9 and Re3Br9 clusters including scalar and spin-orbit relativistic effects (ADF + ZORA + SO). Our calculations have shown that both the clusters exhibit aromaticity and that spin-orbit effects decreases aromaticity due to the fact that the 5d(3/2) spinors are mostly occupied and are more contracted than the scalar 5d orbitals. (C) 2008 Elsevier B.V. All rights reserved.