A congenital cystic adenoid malformation of the lung(CCAM) is characterized by an anomalous fetal development of the terminal respiratory structures, resulting in the adenomatoid proliferation of the bronchiolar elements and cystic formation. CCAM has been detected on the fetus, premature babies and stillborn as well as infants and children. An adult presentation of CCAM is extremely rare. When cystic lesions occur with a repeated infection, an evaluation of the cystic lesions requires a differential diagnosis of CCAM, sequestration, a lung abscess, a pneumatocele and a bronchogenic cyst. The definite treatment of CCAM is the surgical removal of the involved lobe. We report a case of a CCAM in a 24-year-old female with a brief review of the relevant literature.