Magnetic semiconductors such as Cu(x)Mg(1-x)O, which are perspective materials for high-temperature superconductivity have been studied by EXAFS. The new technique of obtaining information from EXAFS-data has been described. It is based on the special iterative algorithm of solving an inverse ill-posed problem on the determination the partial pair correlation functions (pPCFs). Bond lengths of the nearest neighbours have been determined. It was clearly shown that the short range order in compound Cu0.2Mg0.8O differs from a hypothetical alloy with MgO structure and from the copper oxide.