An important environmental problem related to the use of fossil fuels is the formation of soot during combustion. Mechanisms of soot oxidation, which alleviates its emission into the environment, are not fully understood. The reaction of O with a radical C15H9 may play an important role in combustion. In this article, the C15H9 molecule was chosen as a model of soot surface. The paper discusses various pathways resulting from the C15H9 + O reaction. Relative energies, frequencies and optimal geometries of the reactants, products, intermediates and transition states of the C15H9 + O reaction have been calculated using the quantum-chemical Gaussian and Molpro program packages. The reaction pathways leading to carbon monoxide CO elimination have been found and dscussed.