Cognitive development in Dravet's syndrome is accompanied by a slowing or stagnation of the cognitive abilities during childhood. The fact that the syndrome is classified within the group of epileptic encephalopathies suggests that the epileptiform activity plays an important role in the genesis of the cognitive disorders. In this review it is shown that the epileptic phenotype and the critical and intercritical activity do not, by themselves, explain the cognitive development in children with Dravet's syndrome. Substantial changes in the treatment, with impact on cognitive development, will probably come with therapies that act by directly modifying the pathophysiology of the syndrome rather than its consequences.