This review examines the neurodevelopmental contribution to the cognitive and behavioural complications of epilepsy. Following a brief review of the lifespan complications of childhood epilepsies, attention turns to cognitive, psychiatric and social correlates of childhood epilepsies reported in population-based and tertiary care studies. The focus then becomes the neurobehavioural status of children with new-onset epilepsy; a point in time not confounded by the effects of years of recurrent seizures, medications, and social reactions to epilepsy. Recent research shows that abnormalities in cognition, brain structure and behaviour are present at or near the time of diagnosis. Further, careful history taking indicates that neurobehavioural problems may be present in advance of the first seizure suggesting the potential influence of epileptogenesis, antecedent neurodevelopmental abnormalities, genetic and environmental susceptibilities, and other risk factors. This becomes the substrate upon which to characterise the effects of epilepsy and its treatment on subsequent neurodevelopment. The review concludes with suggestions for future clinical care and research.