We describe 3 patients with different degrees of cerebellar hypoplasia and continuous spike-waves during sleep: the more extensive the cerebellar hypoplasia, the more compromised the neuropsychological abilities and behavior. Cerebellar hypoplasia is a risk factor for epilepsy and/or neuropsychological and psychiatric disorders. Epilepsy is also strongly associated with familial antecedents for seizures, as previously reported. The cerebellum is implicated in controlling epileptic seizures and in regulating motor, cognitive, and emotional functions with a topographic organization. The association between cerebellar hypoplasia and continuous spike-waves during sleep has never been reported. We suggest that continuous spike-waves during sleep may further compromise neuropsychological and behavioral features that are associated with cerebellar hypoplasia.