This study investigated the nature of resources involved in duration processing in 5- and 8-year-olds. The children were asked to reproduce the duration of a visual or auditory stimulus. They performed this task either alone or concurrently with an executive task (Experiment 1) or with a digit or visuospatial memory task (Experiment 2). The results showed that duration reproduction was systematically shorter in the dual-task condition than in the single-task one. Furthermore, timing an auditory stimulus decreased the proportion of accurate responses in the executive and digit memory tasks but not in the visuospatial memory task, whereas timing a visual stimulus decreased the proportion of accurate responses in the executive and visuospatial memory tasks but not in the digit memory task, at least to a lesser extent in the older children. This pattern of interference suggests that duration reproduction in children requires both the central executive and the slave memory system associated with the modality of the temporal stimulus. (Contains 4 figures and 2 tables.)