In an N-atomic polyatomic molecule there are 3N-6 vibrational coordinates (3N-5 for a linear molecule) that enter into the electronic Hamiltonian as parameters. For a diatomic molecule there is only one such coordinate, the bond length r. Thus, due to the avoided crossing theorem, in a diatomic molecule we cannot have level crossings between electronic states of the same symmetry. However, for a polyatomic molecule there is more than one geometry parameter in the electronic Hamiltonian and level crossings between electronic states of the same symmetry are not avoided.