Radiograph and CT of a nearly two-year-old young boy with necrotizing pneumonia. The chest radiograph (a) shows several cystic lucencies within the opacified lung, visulaized on CT as multiple cavities, the largest of these at the bases. The lung parenchya is notably hypodense despite administration of intravenous contrast medium, indicating the presence of necrotic areas. Vessels are poorly seen. A pneumatocele is seen as a residuum approx. 8 weeks later (b).