BACKGROUND: Congenital cystic adenomatoid malformation of the lung (CCAM) is a rare congenital developmental anomaly of the lower respiratory tract. Most cases are diagnosed within the first 2 years of life, so adult presentation of CCAM is rare. We describe here six adult cases of CCAM and the patients underwent surgical resection, and all these patients were seen during a five and a half year period. The purpose of this study was to analyze the clinical, radiological and histological characteristics of adult patients with CCAM. METHODS: Through medical records analysis, we retrospectively reviewed the clinical characteristics, the chest pictures (X-ray and CT) and the histological characteristics. RESULTS: Four patients were women and the mean age at diagnosis was 23.5 years (range: 18~39 years). The major clinical presentations were lower respiratory tract infection, hemoptysis and pneumothorax. According to the chest CT scan, 5 patients had multiseptated cystic lesions with air fluid levels and one patient had multiple cavitary lesions with air fluid levels, and these lesions were surrounded by poorly defined opacities at the right upper lobe. All the patients were treated with surgical resection. 5 patients underwent open lobectomy and one patient underwent VATS lobectomy. On the pathological examination, 3 were found to be CCAM type I and 3 patients were CCAM type II, according to Stocker's classification. There was no associated malignancy on the histological studies of the surgical specimens. CONCLUSION: As CCAM can cause various respiratory complications and malignant changes, and the risks associated with surgery are extremely low, those patients who are suspected of having or who are diagnosed with CCAM should go through surgical treatment for making the correct diagnosis and administering appropriate treatment.