Computed tomography and magnetic resonance imaging are now commonly performed for a variety of pulmonary and mediastinal lesions. However, some of the lesions that affect these areas also involve the chest wall. These include tumors, infections, trauma, and congenital processes. In such cases, a knowledge of chest wall anatomy combined with careful analysis of cross-sectional images is necessary to make the diagnosis. This article describes the basic cross-sectional anatomy of the chest wall and the principal pathologic chest wall lesions.