Ab initio MO calculations at the MP2/6-31G* level indicate a nonplanar structure (1) to be the favored arrangement for B-3(mu-H)(3)X(3)(+) (X = H, F, and Li). In contrast, B-3(mu-Li)(3)H-3(+) (2) is calculated to be a minimum in the planar arrangement. The structural preferences of 1 and 2 are explained from their molecular orbital pattern and charge distributions.