Cystic adenomatoid malformation is an uncommon embryonic developmental abnormality usually diagnosed in neonates and infants. Its presentation in adulthood is rare, with only 27 cases reported up to now. Due to its rarity, it is seldom suspected and adult physicians are not familiar with its clinical and radiologic features. We report two cases of cystic adenomatoid malformation presenting in adults, one as a recurrent pneumonia, and another as a coincidental finding on a chest roentgenogram. We describe the clinical features, radiologic and computed tomographic findings, and the histopathologic characteristics in this article, along with a review of the literature.