Four reaction channels for the title reaction were theoretically studied at the B3LYP/6-311++G(d,p) theory level. At 298.15 K the most favorable route to HCO + NO (reaction 1) is the singlet one with an energy barrier of 15.3 kcal/mol in close agreement with the reported value of 15.0 kcal/mol. Both the singlet and the triplet pathways to yield CO + NO + H (reaction 2) are kinetically competitive with an energy barrier of 20.7 kcal/mol. The triplet channels to HNCO + O (reaction 3) and to NCOH + O (reaction 4) present an energy barrier at 298.15 K of 11.5 and 29.6 kcal/mol, respectively, whereas those for the corresponding reverse processes are 16.2 and 5.9 kcal/mol to compare with the reported values of 11.4 and 4.0 kcal/mol, respectively. Except for reaction 2 the rate determining TSs remain the same at higher temperatures. The tripler pathway to HNCO + O is the most favored one at the three temperatures considered in this work: 298.15, 1000, and 1500 K, At higher temperatures reaction 4 remains the most disfavored kinetically but the Gibbs energy barriers for reactions 1-3 become closer the higher the temperature so that at 1500 K reactions 1 and 2 are competitive with reaction 3. These trends would agree with the increase of the concentration of NO and the decrease of the concentration of HNCO found experimentally. It is interesting to note that reaction 2, which has been found to be a high rate and sensitive reaction by reaction-path analysis, is the most kinetically favored one by an increase of temperature.