Ion channeling along the c-axis of YBaCuO single crystals revealed anomalies at Tc, which were attributed to a different dynamical behaviour of the Cu atoms in the normal and the superconducting state.1,2Using the O16(α/α)O16resonant scattering at 3.05 MeV we observed additional anomalies in the O-sublattice.3The latter experiments were performed on c-axis oriented single crystals and on a- and c-axis oriented thin YBaCuO films. The experimentally observed dependences of the angular yield curves on the temperature and on the tilt plane could be well reproduced by Monte-Carlo (MC) simulation calculations. Several displacement models have been used to simulate the structural distortions in the Cu- and O-sublattices at Tc. The most probable model is the assumption of structural distortions in the Cu- and O-sublattice above Tc, which relax below Tc. The change in the total displacement amplitudes is about 0.4 pm for the Cu- and about 2 pm for the O-sublattice.