Abstract: Methanethiol and hydrogen sulphide photooxidation reaction pathways contain stages of hydrogen transfer, after which intersection crossing supposed to be to achieve singlet products of the reaction. While studying this stages no minimum was found at the point near reactants in the singlet state. At the same time there is a minimum in the triplet state. Moreover energy of reactants in the singlet state exceeds energy in the triplet state. That observation allows us to suppose intersection between the singlet and the triplet potencial energy surfaces at the hydrogen transfer stage. It may increase chance of the triplet-singlet transition. Calculation of the potencial energy surface profiles, sliced along with the hydrogen transfer path for both the singlet and the triplet states, performed with UB3LYP 6-311G++(d) method of the density functional theory have showed both existence and reaction coordinate of intersection.