Molecular and kinetics properties of the FS(O-2)OCO radical have been studied. Equilibrium structure, harmonic vibrational frequencies, conformational mobilities, enthalpy of formation of this radical and the energetic of the reaction FSO3 + CO -> FS(O-2)OCO have been investigated at different levels of the density functional theory and of the Gaussian composite models. The standard enthalpy of formation for FS(O-2)OCO is predicted to be Delta H-f,H-298 = -155.0 kcal mol(-1). In very good agreement with reported experimental values, a rate coefficient at 296 K of 3.6 x 10(-17) cm(3) molecule(-1) s(-1) and an activation energy of 7.6 kcal mol(-1) have been calculated. (C) 2010 Elsevier B.V. All rights reserved.