defects in nanostructures seem to play crucial influence on their properties. Twinnings are the most popular 3D defects in II-VI semiconductor compounds having zinc-blende structure (Zn, Cd chalcogenides). These defects are of {111} type. Electron diffraction of such defected crystals as well as nanostructures (thin layers, clusters and other nanoscale individuals) results in satellite spots placed around the main single crystal spots in diffraction pattern. This is due to the different orientation of the matrix and twins of the first and higher orders with respect to the electron beam. Basing on a reciprocal lattice of twinned structure, the interpretation of nature of satellite spots is addressed. The double positioning, primary and double diffraction were described. The considerations were applied to the nanostructured epitaxial CdTe and Hg 1-x Cd x Te layers obtained by laser deposition.