The geometries and spectroscopic constants of the dihalosilanones, F2SiO, Cl2SiO, Br2SiO, and I2SiO, and their cis- and traps-XSiOX isomers were calculated by high-level computations. The potential energy surfaces of the isomerization reactions were investigated and the transition-state structures determined, together with the isomerization and activation energies and enthalpies. It was shown that, in contrast to silanone and the hydroxysilylenes, the dihalosilanones are much more stable than their other structural isomers. Thus, even at several thousand kelvin temperatures, a common condition inside a metal halide lamp, the presence of appreciable amounts of the cis- and traps-BrSiOBr and ISiOI isomers is unlikely.