Thoracic imaging is widely used to detect lower respiratory tract infections, identify their complications, and aid in differentiating infectious from noninfectious thoracic disease. Less commonly, the combination of imaging findings and a clinical setting can favor infection with a specific organism. This confluence can occur in cases of bronchiectatic nontuberculous mycobacterial infections in immune-competent hosts, invasive fungal disease among neutropenic patients, Pneumocystis jiroveci pneumonia in patients with AIDS, and in cytomegalovirus infections in patients with recent hematopoietic cell transplantation. These specific diagnoses often depend on computed tomography scanning rather than chest radiography alone.