Semiempirical and ab initio molecular orbital methods, including full geometry optimizations, are used to study the rotational profile about the central CC bond of perfluorobutadiene. The MNDO method yields a rather flat potential with a minimum of 109°, corresponding to a nearly perpendicular arrangement of the two CC bonds. The potential calculated by both PRDDO and ab initio with a minimal STO-3G basis set contains two minima. One of these is a nonplanar cisoid type structure corresponding to the experimentally observed conformation. Slightly lower in energy is a planar structure with the two double bonds trans to one another.