The results of a theoretical study of the molecular structure and conformational mobilities of the peroxynitrate CF2BrCFBrOONO2 and its radical decomposition product CF2BrCFBrOO are reported in this paper. The most stable structures were calculated from ab initio G3(MP2)B3 and G4(MP2) methods and from density functional theory at the B3LYP/6-311+G(d) and B3LYP/6-311+G(3df) levels of theory. The equilibrium conformation of CF2BrCFBrOONO2 indicates that the bromine atoms lie in position anti to each other and possess a COON dihedral angle of 114 degrees. A quantum statistical analysis shows that about 40% of the internal rotors can freely rotate at room temperature. Our best values for the standard enthalpies of formation of CF2BrCFBrOONO2 and CF2BrCFBrOO at 298 K obtained from isodesmic reactions at the G3(MP2)//B3LYP/6-311+G(3df) level of theory are -144.7 and -127.0 kcal mol(-1). From these values and the enthalpy of formation of the NO2 radical, a CF2BrCFBrOO-NO2 bond dissociation enthalpy of 26.0 +/- 2 kcal mol(-1) was estimated.