The cerebellum is involved in motor and cognitive functions and behavior. Its role in controlling epileptic seizures has been demonstrated in the literature. Genetic factors can enhance epilepsy susceptibility when the cerebellum is damaged. We examined the occurrence and features of epilepsy, intelligence, and psychiatric disorders in 28 patients with cerebellar hypoplasia. We compared patients with (10; 35.7%) and without (18; 64.3%) epilepsy. The statistical evaluation showed a significant prevalence of familial antecedents for seizures in patients with epilepsy (P < .01); cerebral associated lesions and type of cerebellar hypoplasia did not influence the occurrence of epilepsy, which was partial in 80% of cases. Profound mental retardation prevailed in patients with epilepsy (P < .05). Both mental retardation (75%) and pervasive developmental disorders (17.8%) prevailed in our cases with respect to the general population (P < .000). Cerebellar hypoplasia in our sample seems to be an important risk factor for the occurrence of epilepsy, mental retardation, and psychiatric disorders.