X‐ray Bragg reflection widths and reflectivities are calculated by the dynamical scattering theory. Results on the binary II‐VI semiconductors CdTe, HgTe, and the ternary alloys CdHgTe and CdZnTe are reported. For comparison, results on several III‐V compounds are also reported. The dependence of the reflection widths and reflectivities on alloy composition, wavelength, layer thickness, and material properties are discussed. Especially in alloys, interesting effects, such as drastic changes of the reflectivity depending on the alloy composition, appear. The behavior of the widths and reflectivities can be understood by the examination of the competing processes of absorption and extinction. The results from calculated intrinsic reflex profiles are compared with approximation formulas.