The paper presents the results of studies on the effectiveness of the shot peening process for thin-walled parts based on the diameter of impressions produced by the impact of shot media. It is also described the current applications of this treatment for the thin-walled parts. The authors described an innovative measuring device which was used in the research. The material used in the studies was non-alloy steel C45. The relationships between beads diameter and thickness of workpieces on diameter of impression were presented.