Abnormalities of the central airways may produce symptoms such as cough, dyspnea, wheezing, or stridor, but there is frequently a delay in diagnosis. If central airways abnormalities are clinically suspected, furthur evaluation of tracheobronchial lesions is best performed with CT. A variety of diseases may affect the airways, resulting in either focal or diffuse narrowing or enlargement. This pictorial essay focuses on diffuse abnormalities of the major airways. We recognize that the distinction of diffuse from focal airway abnormalities is somewhat arbitrary and is complicated by the fact that many diseases can cause either focal or diffuse airway narrowing. For purposes of this review, however, we will discuss only those diseases that most commonly result in long-segment or multifocal airway disease.