Half integer superlattice reflections characteristic of ordered structure in PMN (Pb(Mg1,3Nb2,3)O3) single crystal have been measured using resonant synchrotron x-ray scattering near the Pb LIII absorption edge. These superlattice peaks have been previously reported in PMN by electron diffraction, and were interpreted in the context of a two phase Nb/Mg ordering model to explain its relaxor ferroelectric behavior. Nevertheless, the microscopic origin of the superlattice peaks is controversial. Previous results have shown that the Nb atom contributes heavily to the superlattice peaks. However, the effective scattering factor for these peaks is significantly smaller than in the case of complete ordering. In addition, there is strong evidence that lead participates in the ordering.