We report on the structural characterization by Rutherford backscattering spectrometry in channeling geometry of CdS epitaxial layers grown on the highly lattice-mismatched CdTe substrates by chemical vapor deposition. The overall layer quality has been investigated for different CdS thicknesses, as well as the occurrence of small misalignments of the crystallographic directions from point-to-point in the layers. A crystallographic study of the hexagonal (wurtzite) lattice is also presented: two principal planes parallel to the c axis have been determined experimentally, i.e., (1010BAR) and (1120BAR), together with their inplane axial directions. This allows investigation of the occurrence of 30-degrees rotation effects in the crystal lattice as observed by scanning electron microscopy.