The lattice dynamics of high-Tc EuBCO superconductor was studied by means of Mössbauer spectroscopy of the 151Eu ion in samples with oriented grains. Three samples were prepared: one oriented by means of 8 T magnetic field, another by means pressure; the third was left random. The orientation distribution function was determined be means of X-ray diffraction. By comparison of the absorption areas of the oriented samples with respect to the random one, the Lamb–Mössbauer factor ratio corresponding to the motions in c-direction and ab-plane was determined. This ratio turned out to be independent of the temperature and of value 0.25±0.05. This very small value can be explained only if a strong anharmonicity is present, which mainly concerns the c-direction motion.