Congenital cystic adenomatoid malformation (CCAM) is a rare lung lesion that may be diagnosed antenatally by ultrasonography. It is believed to result from an arrest in lung development. The differential diagnosis of a mass in the fetal thorax includes CCAM, congenital diaphragmatic hernia, and pulmonary sequestration. This brief review discusses classifications of CCAM with images of each type, sonographic findings, factors that affect the prognosis, and important aspects of management once the diagnosis is made. (Source: Journal of Diagnostic Medical Sonography)