The geometries, vibrational spectra, and relative energetics of CXBrO have been examined using density functional theory. The results show interesting structural trends for the bromination of formaldehyde. The thermodynamically most stable species is found to be CClBrO, with an estimated heat of formation of -38.2 kcal mol(-1) at 298 K. The least stable CXBrO species is CBr2O with a heat of formation of -25.8 kcal mol(-1) at 298 K. The heat of formation of CBr2O is in excellent agreement with experiments which determine the value from third-law kinetic studies.