Ab initio molecular orbital calculations at the QCISD(FULL)/DZ+P level of theory were carried out on the hydrogen trioxides H2O3 and H2O/O-2 (O-2 is (3) Sigma(g)(-)) and their Li+ ion and proton adducts to determine the binding energies (Li+ affinity-and proton affinity) for H2O3-Li+ and H2O-Li+-O-2. Calculations include the thermochemistry at 298K and enthalpy corrections for comparison with experimental values. Our prediction for the binding energy of Li+ to H2O3 is 33.0 kcal/mol, which closely resembles that between Li+ and homologous molecules of water and H2O2. In the case of the H2O-Li+-O-2 system, the process may be that a primary product of H2OLi+ would then bind to oxygen (or O2Li+ to water). Binding energies of H2OLi+ or Li+ to O-2 are 8.6 or 5.2 kcal/mol, respectively, which are smaller than those required for adduct formation under conventional experimental conditions. The overall results suggest the validity of our recent experimental detections of Li+ ion attachment to hydrogen trioxide. But the detection of the H2O-Li+-O-2 complex may not be possible.