Temperature dependent studies of the 1/2(hk0) superlattice reflections (&agr; spots) by synchrotron x‐ray scattering measurements were performed in Pb(Mg1/3Nb2/3)O3(PMN) and [PbMg1/3Nb2/3O3]1−x‐ [PbTiO3]x(PMN‐xPT) with Ti dopingx⩽ 0.32 single crystals. Separation of the &agr; spots from the underlying diffuse scattering background allowed studying them as separate entities for the first time. Structure factor calculations have shown that &agr; spots constitute the presence of a new kind of anti‐ferrodistortive nanoregions (AFR) in the form of fluctuations produced by anti‐parallel short‐range correlated ⟨110⟩ Pb2+displacements. AFR appear to be different and unrelated to the chemical nanodomains (CND) and ferroelectric polar nanoregions (PNR). Simultaneous presence of AFR and PNR can explain relaxor behavior as a result of competition between randomly occurring ferroelectric and anti‐ferroelectric fluctuations. Temperature dependence of the &agr; spots in PMN showed a direct correlation with the freezing phase transition near Tf≈220 K. © 2003 American Institute of Physics