This study tested the modality effect on time judgment in a bisection task in children and adults when auditory and visual stimuli were presented in the same session. Cognitive capacities of children and adults were assessed with different neuropsychological tests. The results showed a modality effect, with the auditory stimuli judged longer than the visual stimuli. However, this modality distortion in time judgment was higher in the younger children. Statistical analyses revealed that the size of this time distortion was directly related to individual working memory capacities.