The interrelationships between brain, cognition, and behaviour are complex but can be more clearly characterised by studying disorders with an underlying genetic basis. This thesis examined these interrelationships in the context of Williams syndrome (WS), a neurodevelopmental genetic disorder that affects aspects of cognition, behaviour, and brain structure. The principal aims of this thesis were to evaluate the cognitive, behavioural, and neuroanatomical profile of WS individuals and to explore the relationships between aspects of the cognitive and behavioural profile and the neuroanatomical changes that are evident in WS. Three general hypotheses, and 10 specific hypotheses, were postulated as a means of exploring these aims. The first general hypothesis predicted that WS individuals would demonstrate distinct features within their cognitive and behavioural profile. Specifically, it was predicted that WS individuals would show relative strengths on verbal tasks and significant deficits on visuospatial and mathematical tasks, in contrast to control participants who were predicted to show a more even profile. It was also predicted that WS individuals would show evidence of heightened affect in response to music and demonstrate hypersociability as compared to control participants