AbstractIntroduction: Working memory is one of the most fundamental cognitive processes underlying thinking and learning. Auditory and visual working memory have similar and different infrastructures that evolve in different ages. The aim of the present study was to investigate the evolution of auditory and visual working memory in primary school-aged children.Materials and Methods: This comparative, cross-sectional study was conducted on 180 students from six grades of primary school selected by available sampling. Auditory and visual working memory performances were assessed by N-back test. Two way anova was used for data analysis.Results: There was significant difference between auditory and visual working memory and aging (p<0.001). The performance speed increased with age in auditory task (p<0.001), while there was no significant difference in visual performance speed in different age groups. No meaningful relationship was found between gender and memory scores.Conclusion: The auditory and visual working memory performances improve with age in primary school children, suggesting functional maturation of underlying cognitive processes and brain areas, but gender not affecting memory performance.Key words: working memory, development, student, N-back task.