The preparation of nanostructured materials is quite often controlled with the help of reflection high energy electron diffraction (RHEED). However, the interpretation of RHEED results should be carried out with some care because electrons strongly interact with atoms. Here, the importance of the refraction effects is shown theoretically. Results of dynamical and kinematical calculations of RHEED rocking curves are compared for diamond and gallium arsenide. Dynamical calculations are carried by solving the Schrodinger equation. For kinematical calculations respective analytical formulas are used. RHEED intensities for growing surfaces are analyzed. In particular, it discussed why the refraction effects are very important for the appearance of RHEED oscillations. (C) 2016 Elsevier B.V. All rights reserved.