XPS techniques are used for a CoMparative study of ion induced effects in simple oxides (ZrO2, SiO2, TiO2) and complex oxides (ZrSiO4, CaTiSiO5, La2TiO5, PbTiO3). We have found that reduction effects in simple and complex oxides differ. The interpretation of altered layer composition has been qualitatively considered in terms of the preferential loss of oxygen and reverse chemical reactions.