There can be many diagnostic pitfalls in the evaluation of the aortopulmonary window by chest radiography alone. Large masses that are easily identified on computed tomography may be essentially undetectable; also the appearances of aortopulmonary window lesions on conventional radiographs are frequently nonspecific, or may even be misleading. Careful evaluation of this region of the mediastinum is important because the aortopulmonary window is commonly the site of adenopathy secondary to neoplastic and inflammatory diseases, as well as vascular pathology. After review of the normal anatomy of the aortopulmonary window, seven selected cases are presented that demonstrate the importance of computed tomography in arriving at the correct diagnosis when conventional chest radiographs are nonspecific or equivocal. © 1987.