In this work, we consider the experimental and theoretical results of studies of the formation of defects on the surface of LiF crystals under irradiation with ions using total current spectroscopy and the SRIM software package. A comparative study was carried out with ions of different masses, and inconsistencies of the occurring physical phenomena between our early concepts were found. It is shown that in the case of heavy ions irradiation, they are implanted and appear substitutional atoms into the bulk of the crystal. For ions with the smallest ion mass, the distribution of interstitial defects is greater on the surface than in the bulk of the crystal. An attempt is made to explain the formation of some defects on the surface (formed peaks in the total current spectra) by the method of computer simulation. Highlights Formation of defects on the surface of LiF films at ions irradiation. Influence of irradiation ions mass on the formation of surface defects. The different distribution of substitutional atoms on the surface. Formation of vacancies and interstitial defects on the surface of LiF films at ions irradiation.