Introduction: This study has aimed to investigate the relationship between the development of working memory and performance on arithmetic activities. Method: We conducted a 3-year longitudinal study of a sample of 90 children, that was followed during the first, second and third year of primary school. All children were tested on measures of WM components (i. e., (i) phonological loop, (ii) visuospatial sketchpad and (iii) central executive) and arithmetic. Results: Results indicate the relationship between the progressive development of working memory capacity and performance in arithmetic through time. Evidence of this is that the group with higher working memory performance gets better scores in calculus, during the three years of study. Discussion and Conclusion: The discrepancy in scores in calculation increases as the years because of the impact it has on working memory strategies used for solving arithmetic problems.