 It is thought that the intubation depth in small bowel determines the diagnostic yield and the following treatment. The deeper the enteroscopy is advanced into the small bowel, the more lesions may be found and treated. In order to improve the intubation depth of balloon enteroscopy, several methods, such as carbon dioxide insufflation and decompression side tube-equipped device, have been tried and showed positive effects. CO2 insufflation could also reduce severe pain during DBE and residual gas retention after the procedure because of rapid absorption. However, it is not known how much CO2 insufflation can decrease the distention of small bowel and the formation of bowel loops. 