Treatment for moyamoya disease in infants and toddlers is challenging, because of the progressiveness of the disease. Revascularization surgery is the first-line therapy and should be performed as early as possible after diagnosis to prevent additional cerebral infarction. This review describes in detail the changes in the new "Diagnostic Criteria 2021 for moyamoya disease", and discusses the concept of treatment including indirect and combined bypass surgery in infants and toddlers. Surgical technique and perioperative management based on our experience are also precisely described.