Wide-angle x-ray scattering (WAXS) of glassy PET and two samples annealed at 190°C for 15 and 30 min were analyzed by differential radial distribution function (DRDF) methods. The corrected intensity profile of the glassy sample show three peaks at 4.19, 2.13, and 1.19 Å. The sample annealed for 15 min shows splitting of the 4.19 Å peak into three peaks at 3.50 (d100), 3.96 (d110), and 5.21 (mainly d010and unresolved d011-and d-111) Å. Longer annealing for 30 min produces two more peaks at 4.11 (d-111) and 5.40 (d011) Å. Annealing does not affect the peaks at 1.19 and 2.13 Å (which are caused by first and second nearest atoms in the chain). The DRDFs of all three samples are similar in some respects as all show intrachain peaks at ∼ 1.45, 2.45, and 4.05 Å. From theoretical calculations of the intrachain distances and their contributions to the DRDF, the peak at the 4.90 Å in the glassy sample was found to be mainly due to intermolecular distances. Since the peaks above 4.9 Å are relatively weak, only nematic lateral ordering (intermolecular correlations) is present and is limited to 20-40 Å. It is suggested that very distorted paracrystalline lattice is present in the glassy state of PET, which is consistent with the previous conclusions based on dark-field electron microscopy studies. Annealed samples showed that all peaks originally weak in the glassy sample become stronger and slightly shifted to lower r values. In addition new peaks are observed with an intermolecular periodicity of ∼ 5 Å for distances up to 40-50 Å for a total chain to chain correlated distance of 80-100 Å, indicating the presence of a markedly improved ordering of laterally aligned chain segments as a result of improved packing of atoms within the lattice.