Observations of behaviour and research using eyetracking technology have shown that individuals with Williams syndrome (WS) pay an unusual amount of attention to other people's faces. The present research examines whether this attention to faces is moderated by the valence of emotional expression. Method. Sixteen participants with WS aged between 13 and 29 years (mean = 19 years 9 months) completed a dot-probe task in which pairs of faces displaying happy, angry, and neutral expressions were presented. The performance of the WS group was compared to two groups of typically developing control participants, individually matched to the participants in the WS group on either chronological age or mental age. General mental age was assessed in the WS group using the Woodcock-Johnson Test of Cognitive Ability-Revised (WJ-COG-R; Woodcock Johnson, 1989/1990). Results. Compared to both control groups, the WS group exhibited a greater attention bias for happy faces. In contrast, no between-group differences in bias for angry faces were obtained. Conclusions. The results are discussed in relation to recent neuroimaging findings and the hypersocial behaviour that is characteristic of the WS population.