A short review is presented of recent Synchrotron White Beam X-ray Topography (SWBXT) and High Resolution Triple-Axis X-ray Diffraction (HRTXD) studies of defects and distortions in 4H and 6H SiC substrates, homo- and hetero-epitaxial layers grown on these substrates, and devices fabricated in these layers. In the substrates, defects observed include closed-core and hollow-core screw dislocations (micropipes) in 6H and 4H, deformation induced basal plane dislocations in 6H and 4H, and small angle boundaries in 4H. For the hetero-epitaxial layers, consisting of 3C grown on specially prepared 4H and 6H mesas, detailed correlation between the defect content of the mesas and the choice of 3C variant and the subsequent lattice mismatch between heteroepilayer and substrate is presented. A brief review of the application of SWBXT to the understanding of the generation of defects during device performance will be presented.