A detailed study of the stepwise substitution of the chloride ligands in the [Re-3(mu-Cl)(3)Cl-9](3-) (1) anion by water molecules is presented using theoretical methods. Ligand lability as well as the structure and relative stability of the various mono-[Re-3(mu-Cl)(3)Cl-8(H2O)](2-) (2) and dihydro-[Re-3(mu-Cl)(3)Cl-7(H2O)(2)](-) (3a-f) conformers is examined. Clear preferences for the positions of the incoming water ligands are proposed based on calculated energy and vibrational data, which fully agree with the experimental results.