The layered Li1+x (Ni0.425Mn0.425Co0.15)1−xO2 (x =0 and 0.12) materials were prepared by a coprecipitation method. Their structure was investigated using the combination of X-ray and electron diffraction experiments. For both materials (x =0 and 0.12), the electron diffraction patterns revealed an in-plane √3a hex. ×√3a hex. superstructure in agreement with the ordering of the Li+, Ni2+, Ni3+, Mn4+ and Co3+ ions in the transition metal layers. The stoichiometry of these materials was not in agreement with an ideal ordering: the possible presence of point defects or of a domain microstructure was thus discussed. Electron diffraction also revealed that these ordered layers were slightly correlated along the c hex. axis for both materials.