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The structural features of the oxygen sublattice in the YBa 2 Cu 3 O 7 crystals are analyzed based on a comparison of the calculated angular dependence of the yield of resonant nuclear reaction 16 O(α, α) 16 O with the available experimental results obtained for ions with energies of 3.055, 3.06, and 7.6 MeV. It is established that in crystal films there are vacancies in oxygen chains at room temperature, and oxygen atoms are considerably displaced from the equilibrium positions in directions perpendicular to the <001> axis. In thick crystals at temperatures close to the temperature of phase transition into the superconducting state, no large thermal and/or static displacements of oxygen atoms from the equilibrium positions are observed.

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