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 √3ahex. × √3ahex. 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...