A bstract Model estimates are obtained for the influence of Coulomb effects on the ratio of the cross sections for the production of charged and neutral B B ¯ and B * B ¯ * pairs in e + e − annihilation. It is shown that the difference between the masses of charged and neutral mesons obtained under the assumption that this ratio is constant on a scale of the order of the beam energy spread can differ from the true one by δM ∼ 0 . 03 MeV at the energy of Υ(5 S ) and by δM ∼ 0 . 4 MeV at the energy of Υ(4 S ). Thus, the errors given in the PDG for the difference between the masses of charged and neutral B mesons, based on the results obtained at the energy of Υ(4 S ), are strongly underestimated. Similar measurements at the energy of Υ(5 S ) will have an order of magnitude smaller systematic shift for the mass difference. This circumstance should be taken into account when planning future experiments at the B factory in KEK.