Rhabdomyosarcoma (RMS) of the lung is a very rare lesion, but the association with cystic adenomatoid malformation (CCAM) is unlikely to be a coincidence. Although the etiologic factors predisposing infants and children to pulmonary neoplasms are unknown, pulmonary developmental abnormalities may play a pathogenetic role. A case of embryonal pulmonary RMS is described, which was discovered within a congenital CCAM in a 22-month-old child. The hypothesis regarding histogenesis of this neoplasm are also briefly discussed. Because of the risk of malignant change, early removal of the congenital cystic lesions of the lung is advisable.