Objective To investigate the clinicopathologic features of congenital cystic adenomatoid malformation (CCAM) of lung in adults. Methods The clinical and pathological characteristics of two cases of CCAM of lung in adults from November 19, 2012 to February 12, 2014 were analyzed, and relevant literatures were reviewed. Results Both of the two patients were males who were 59 years and 60 years old respectively. Both of them presented with respiratory symptoms such as productive cough, hemoptysis and fever. The lesions in the two cases were about 4.0 cm×3.0 cm×1.5 cm and 5.0 cm×5.0 cm×3.0 cm in size respectively. Both had a cystic appearance and involved unilateral lobes of the lung. Histologically, normal pulmonary alveoli were replaced by different size of cysts composed of adenomatoid hyperplastic bronchioles. The inner cystic wall was lined by pseudostratified ciliated columnar epithelium, and the cystic wall contained smooth muscle and elastic tissue, but no cartilage. In one of our cases, mucous cells could be seen in part of the inner cystic wall, with focal atypical hyperplasia. Conclusions CCAM of the lung is a rare congenital developmental anomaly, which typically manifests in neonates and infants, but extremely rare in adults. The diagnosis of CCAM in adults depends on clinical features, imaging changes and histopathological characteristics.