The oxygen content determines the transport properties of Ba₂YCu₃O_7+x and EuBa₂Cu₃O_7+x, and in particular their superconducting behavior at high temperatures. The authors studied the changes in the Ba₂YCu₃O_7+x electronic structure which are caused by modifications in the amount of oxygen. The modifications were achieved either by thermal annealing or by exposure to white' synchrotron radiation which causes oxygen desorption, with similar results. They found that the decrease in oxygen content affects the line-shape of the upper valence band features and the relative intensity of the Cu satellite features. The lineshape changes simplify the identification of oxygen-related features in the upper valence band region. The exposure to white' synchrotron radiation of Ba₂EuCu₃O_7+x did not produce similarly large spectral changes