The study investigated spatial ability and visuo-spatial memory in groups of high school students with different levels of mathematical fluency. We used the Mental Rotation Task and Corsi Block-Tapping Task to measure spatial ability and visuo-spatial memory, respectively. A statistically significant difference was found between the groups with different levels of math fluency in terms of effectiveness of spatial ability and level of visuo-spatial memory. Statistically significant sex differences were observed in levels of spatial ability and visuo-spatial memory: males showed better results than females. However, sex explained only between 1 and 3% of the variation in these abilities