The structures of B2H5·, B2H5CO·, and B2H5N2· radicals are investigated using the 6–31G* basis set. Both double H-bridged and single H-bridged isomers are found to be local minima on the potential energy surface. The effects of electron correlation are taken into account using single point MP4/6–31G* calculations and, for the diboryl radicals, complete MP3/6–31G* optimizations. In all cases the single H-bridged isomers are found to be more stable than the corresponding double H-bridged isomers.