Acute alternating hemiplegia in childhood is a rare disorder characterized by onset before 18 months of age and frequent attacks of alternating paralysis. In this case report, a 20-month-old boy having the diagnosis of acute alternating hemiplegia is presented. The diagnosis was based on clinical features. The frequency and severity of the hemiplegic attacks decreased following flunarizine therapy. In this case, cerebral perfusion was investigated during ictal and interictal periods. Tc-99m HMPAO-Brain single photon emission computed tomography (SPECT) revealed normal cerebral perfusion in ictal periods and hypoperfusion in interictal periods.