Research on theory of mind (TOM) has provided a major contribution to the understanding of developmental disorders characterized by atypical social behaviour. Yet, there is still little consensus relative to TOM abilities in Williams syndrome (WS). This study used visual and verbal tasks to investigate attribution of intentions in individuals with WS relative to mental age-matched typically developing individuals. Results showed that individuals with WS perform as accurately as controls on the verbal but not on the visual task. Such modality differences did not affect WS group's performance on a control condition not requiring TOM neither were found for the control group. These results suggest the existence of a verbal "peak" and a visual "valley" in TOM ability in WS.