Two series of oxygen deficient perovskites with composition La 0.5 Ca 0.5 MnO 3−δ have been prepared by different synthetic routes. Magnetic measurements indicate that samples with same degree of anionic vacancies (identical δ value) have different behavior. A systematic study of a large set of samples shows that depending on the synthesis protocol followed to induce the anionic vacancies different species of manganese can be stabilized. To confirm this assumption, a detailed XANES study has been carried out together with X-ray diffraction, electron diffraction and thermogravimetric analysis, for a large set of samples. Our results indicate the coexistence of Mn 2+ , Mn 3+ and Mn 4+ species for those samples obtained from a La 0.5 Ca 0.5 MnO 2.5 parent compound. However, only Mn 3+ and Mn 4+ species are stabilized when the synthesis is based on direct reduction of La 0.5 Ca 0.5 MnO 3 . Reduction and oxidation mechanism and magnetic properties are discussed as a function of the Mn oxidation states.