The knowledge of local order in aqueous solutions of electrolytes and the way it changes with temperature and concentration is an important chapter of Chemical Physics of Solutions, some aspects of which are still open and strongly debated. Recently, increasing attention has been devoted to the structure of concentrated aqueous solutions of divalent metal halides, for which qualitative changes in local ordering at increasing concentration are thought to take place. These changes might affect: 1. the details of the structuring occurring around the cations, concerning in particular the possible formation of complexes with the halide ion nearest neighbour to the cation; 2. the possibility that, with increasing concentration a middle or long range order structure appears, which involves strong cation-cation correlation. These two aspects are obviously connected, as the appearance of long range order phenomena should also affect the shorter distance structure around the ions. Results obtained through different experimental techniques seem to give a non unique answer to these structural problems. Since diffraction patterns contain the most direct information about mean molecular configurations in solution, meaningful contributions in clarifying these problems may come from X-ray diffraction studies of different electrolyte solutions at various concentrations. Here, X-ray diffraction data analysis of concentrated aqueous solutions of CdCl 2, NiCl 2 and CaCl 2 are presented, as contribution to the discussions about the problems mentioned above. ▪