The aim of this paper is to investigate the ways in which the number line can function in solving mathematical tasks by first graders (6 year olds). The main research question was whether the number line functioned as an auxiliary means or as an obstacle for these students. Through analysis of the 32 students' answers it appears that the number line functions both as an auxiliary means and as an obstacle with the latter occurring in the majority of cases. (Contains 1 table and 9 figures.)