Abdominal distension is not an uncommon symptom in the neonate; it is indistinguishable from Hirschsprung disease by symptoms and X-ray findings. In three patients, severe abdominal distension was found at early infancy and improved with conservative treatment without relapse. The findings were different from those of Hirschsprung disease. Immaturity or poor coordination of peristaltic movement is postulated as the cause. With maturation such problems can normalize. However the pathogenesis remains unclear and further investigation is needed to improve our understanding.