Objective To discuss the diagnosis and treatment of ductoscopy for intraductal non-protruding lesions. Methods A retrospective analysis was made on characteristics, morphological features, and curative effects of 165 cases of intraductal non-protruding lesions between December 2002 and October 2005. Results Among the 165 cases, there were 135 cases of plasma cell galactophoritis, 18 cases of cystic mastopathy, and 12 cases of galactophoritis. In 144 cases receiving non-surgical treatment, 82 cases were completely relieved and 62 improved. Other 21 cases of plasma cell galactophoritis were surgically treated. Conclusions Mammary ductoscopy is an important way for the diagnosis of intraductal non-protruding lesions. Furthermore, effective treatment can be achieved under ductoscopy in most of cases, and unnecessary surgery may be avoided.