The article describes the application of X‐ray computed tomography to the recording and analysis of ornamentation on the Mesolithic harpoon found at Police in NW Poland. The geometric ornament was divided into eight areas. Based on the tomographic data, a method of quantitative analysis of ornamentation was proposed. For lines selected in individual areas, three profiles were determined for which the width, depth and opening angle of the ornament lines were measured. The analysis of these data, including statistical analyses, revealed a degree of variation, dependent on the engraving technique and the instrument used to make the ornament.