There are many types of diagnostic imaging studies available for the evaluation of foregut duplication cysts. Esophagography may be helpful in confirming the presence of a mediastinal mass, explaining esophageal symptoms, or defining the location of a lesion, but it is rarely diagnostic. Digital subtraction angiography can successfully be used in place of pulmonary arteriography to define vascular anatomy. Computed tomography is often diagnostic, although the attenuation number may be slightly elevated and not that of water. Computed tomography will clarify the relationship of the mass to adjacent mediastinal structures, and may also assist in percutaneous guided aspiration. Surgical resection is often necessary in an infant because of respiratory distress with airway compromise. In asymptomatic patients with a round to oval, nonenhancing, thin walled, cystic mass demonstrated on CT, a thoracotomy may be avoided and the patients may be followed by chest radiography.