Phospholipids are amphiphilic molecules of biological interest as they constitute an integral part of many natural membranes under the form of bilayers. Given the structural complexity of these membranes, phospholipid bilayers are useful model for studying how biologically relevant chemicals affect their structures and functions. Lithium, cadmium and aluminum have been associated to neurological problems which have been related to their interactions with cell membranes. In this paper, the structural effects of Li+, Cd2+ and Al3+ ions on the phospholipids dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE) are reported. These studies were carried out with different concentrations of each cation by X-ray diffraction methods. The results revealed differences in their binding to both phospholipid bilayers. Whereas the structure of DMPE was not perturbed by any of these ions to a significant extent, Cd2+ and Al3+ did interact with DMPC, disordering its molecular arrangement. It was also found that 0.1M and higher concentrations of Al3+ had an ordering effect on DMPC bilayers.