Radiologists have a special role in the management of neutropenic patients. The appropriate investigational technique, frequently targeted differential diagnosis, and the special needs of these patients, need to be understood. Early detection of a focus is the major goal in febrile neutropenic patients. As pneumonia is the most common focus, chest imaging is a special radiological task. The sensitivity of chest X-ray, especially in supine position, is known to be low; therefore, the very sensitive high-resolution CT (HRCT) became gold standard in neutropenic hosts and will probably be replaced by thin-section multislice CT (MSCT) in the near future. Costs of high-resolution CT are low in comparison to antibiotics. An infiltrate needs to be localised, so that a physician can utilise this information as a guidance for invasive procedures for further microbiological work-up. The radiological characterisation of infiltrates gives a first and rapid hint to differentiate between different sorts of infectious (typical bacterial, atypical bacterial, fungal) and non-infectious aetiologies. Follow-up investigations need careful interpretation according to disease and concomitant treatment. Due to an increased incidence of fungal infiltrates even with appropriate therapy, follow-up of an infiltrate must use further parameters in addition to lesion size. Temporary exclusion of infectious involvement of the lung with high accuracy remains of special interest for clinicians.