Unreduced small bowel intussusception requires operative treatment although the rate of spontaneous reduction is 60 to 70%. The aim of this study is to compare clinical characteristics and outcome between spontaneous reduction and operation group and to analyze factors related to decisions to treat small bowel intussusceptions. The records of 25 patients with small bowel intussusceptions treated in Seoul National University Children's Hospital from January 1999 to August 2009 were reviewed respectively. Spontaneous reduction group (n=12, 48%) had signs and symptoms of vomiting, abdominal pain, currant jelly stool, abdominal distension, fever, increased CRP but no rebound tenderness. One of them had been diagnosed with Henoch-Schonlein purpura and no one displayed pathologic leading point by image study. Operation group (n=13, 52%) consisted of patients who had primary surgery. Their signs and symptoms were similar to spontaneous reduction group. Seven of them had underlying diseases such as Crohn' disease, ALL, Lymphoma, Peutz-Jeghers syndrome (n=3), post-transplanted state of liver and 2 of them displayed Peutz-Jeghers polyp and Meckel's diverticulum as pathologic leading point by preoperative ultrasonography. Mean relieve interval (interval between onset of symptoms and reduction/operation) was 1.78 days in spontaneous reduction group and 2.25 days in operation group (p=0.341). Seven of operation group had manual reduction and 6 out of 7 received segmental resection of the small bowel. No one of them underwent manual reduction and all of them underwent segmental resection were found to have pathologic leading points [Peutz-Jeghers polyp (n=3), Meckel's diverticulum (n=2), lymphoma (n=1)] during operation. In conclusion, 48% of small bowel intussusceptions resolved spontaneously. Patients' symptoms and relieve intervals were not related to the operative decisions. We therefore recommend significant factors for determining treatment plan such as change of clinical symptoms, underlying disease or pathologic leading point by imaging.