The structure of poly(vinylidene fluoride) (PVF2) and vinylidene fluoride-tetrafluoroethylene (VF2-VF4) copolymer blends has been investigated by wide angle X-ray scattering (WAXS) study. Blends of two PVF2 samples (KF, H-H defect=3.5 mol% and KY, H-H defect=5.3 mol%) and two copolymers (Cop-1, Cop-2, H-H defect=15.8 and 21.3 mol%. respectively) were crystallized at 30 degrees C, 120 degrees C and 156 degrees C (130 degrees C for copolymers). From the WAXS results it has been observed that both the KF/KY PVF2 and Cop-1/Cop-2 blends cocrystallize at all the temperatures in the alpha and beta phases, respectively. However, in the KF/Cop-1 or in the KY/Cop-1 blends cocrystallization is not found for all the compositions of the blends. In PVF2 rich compositions a phase cocrystals were found and in Cop-1 rich compositions both alpha and beta polymorphs were found. The latter results indicate the absence of cocrystallization at the Cop-1 rich compositions for both the systems. The results support the theoretical prediction of crossover point composition from alpha to beta phases, particularly for systems where cocrystallization is occurring. The spacing d(hkl) increases with H-H defect for both the phases at all temperatures, but the rate of its increase with H-H defect is maximum for crystal lization at 120 degrees C. Further the rate of increase of d(hkl) eith H-H defect is more for beta phase than that for alpha phase and has been attributed to the more compact nature of beta unit cell. The lattice parameters for zero% H-H defect PVF2 measured from the least square intercept of d(hkl) vs H-H plots are somewhat higher than the values predicted from the theoretical calculations by Farmer et al.