Asthma is one of the most common diseases of the lung. Asthma manifests with common, although often subjective and nonspecific, imaging features at radiography and high-resolution computed tomography. The primary role of imaging is not to make a diagnosis of asthma but to identify complications, such as allergic bronchopulmonary aspergillosis, or mimics of asthma, such as hypersensitivity pneumonitis. This article reviews the imaging features of asthma as well as common complications and mimics.