Background: Autism and Williams syndrome (WS) are neuro-developmental disorders associated with distinct social phenotypes. While individuals with autism show a lack of interest in socially important cues, individuals with WS often show increased interest in socially relevant information. Methods: The current eye-tracking study explores how individuals with WS and autism preferentially attend to social scenes and movie extracts containing human actors and cartoon characters. The proportion of gaze time spent fixating on faces, bodies and the scene background was investigated. Results: While individuals with autism preferentially attended to characters' faces for less time than was typical, individuals with WS attended to the same regions for longer than typical. For individuals with autism atypical gaze behaviours extended across human actor and cartoon images or movies but for WS atypicalities were restricted to human actors. Conclusions: The reported gaze behaviours provide experimental evidence of the divergent social interests associated with autism and WS.