Many posterior fossa malformations are associated with other malformations particularly supratentorial ones, which tend to affect the prognosis of these patients. The role of the cerebellum in higher learning is just beginning to be understood, but it is obvious that cerebellar abnormalities may result in higher-cognition defects. Studies have demonstrated cerebellar abnormalities in patients with developmental encephalopathies, such as autism, mental retardation, and Rett syndrome. Disorders that affect cell life cycles and result in abnormal cell proliferation and abnormal cell migration disorders (hemimegalencephaly, dystroglicanopathy, lissencephaly, and gray matter heterotopia) can also be accompanied by posterior fossa malformations. In this article, we discuss hindbrain-midbrain malformations associated with developmental encephalopathies and with supratentorial brain abnormalities that result from abnormal cell proliferation and cell migration.