Objective: To study the clinical characteristics of childhood- and adolescent- onset hypoparathyroidism. Methods: The clinical data of 128 hypoparathyroidism patients with onset before the age of 18 years were collected and analyzed retrospectively. Results: The predominant features of the hypoparathyroidism were carpopedal spasm (89.3%, 108/121) and seizures (66.1%, 84/127). Intracranial calcification was identified in 89.4%(101/113) of the patients. Duration is an independent predictive factor (OR=1.483, P=0.011) for intracranial calcification. All the patients were treated with calcium and vitamin D or its metabolites. Hypercalciuria was associated with serum calcium (P=0.016). Conclusions: Carpopedal spasm and seizures were the main manifestations of childhood- and adolescent- onset hypoparathyroidism. Calcium and vitamin D or its metabolites are effective. Monitoring the concentration of serum and urinary calcium is of highly importance for the prevention of hypercalciuria.