The molecular structure of closo-9,12-(SH)2-1,2-C2B10H10 has been determined by the concerted use of quantum chemical calculations and gas electron diffraction (GED). For the purposes of GED, the architecture of the carbaborane cage was simplified to allow it to have C2v symmetry, while the positioning of the thiol groups means that the molecule had overall C1 symmetry. The accuracy of the experimental structure, as well as that calculated at the MP2(full)/6-311++G(3df,3pd) level, has been gauged by comparison of experimental (11)B NMR chemical shifts with those calculated using gauge-invariant atomic orbitals (GIAO) methods. The inclusion of electron correlation in the magnetic property calculations (GIAO-MP2) gave superior results to those carried out using GIAO-HF. The electronic structure of this derivative, with respect to its directional interaction with a metal surface, is outlined.