In treating cases of malignancy, the use of chemotherapy carries a high risk of lower respiratory tract infections, especially fungal pneumonopathy. This complication is a major cause of mortality and is often difficult to diagnose because of non-specific clinical or radiological changes, but the early recognition of invasive fungal disease is imperative. CT is an important non-invasive method for the detection and evaluation of opportunistic fungal infections. In these patients an improved survival rate can be achieved when early detection by CT leads to the prompt institution of high-dose antifungal therapy. We illustrate the spectrum of CT findings of invasive pulmonary aspergillosis encountered in children with cancer. These patients had previously been treated with high-dose chemotherapy with or without bone marrow rescue, and underwent radiological examinations because of clinical evidence of pneumonopathy. Representative cases demonstrate the clinical applications of CT in the evaluation and management of invasive fungal disease.