The importance of improving and raising the understanding of core concepts in mathematics is well known. Geometry, along with sets, algebra, data and probability, is one of the basic mathematics fields taught in primary and high schools. We have noticed that lately, students' results in geometry are much worse than the results in other mathematical fields. One of the proven methods for improving teaching geometry is harmonising the learning process and content presented in school with the level of understanding on which students are. The mentioned method is based on Van Hiele theory. In order to monitor the effectiveness of the method, it is necessary to assess the level of understanding of students periodically. On the other hand, Comparative Judgment as an assessment method is efficient, fast, and has good outcomes. Our research aimed at investigating whether the Comparative Judgement method can be used to predict the level of understanding of geometric concepts according to the Van Hiele theory.