The severely ill infant or child who requires admission to a pediatric intensive care unit (PICU) often presents with a complex set of problems necessitating multiple and frequent management decisions. Diagnostic imaging plays an important role, not only in the initial assessment of the patient's condition and establishing a diagnosis, but also in monitoring the patient's progress and the effects of interventional therapeutic measures. Bedside studies obtained using portable equipment are often limited but can provide much useful information when a careful and detailed approach is utilized in producing the radiograph and interpreting the examination. This article reviews some of the basic principles of radiographic interpretation and details some of the diagnostic points which, when promptly recognized, can lead to a better understanding of the patient's condition and thus to improved patient care and management. While chest radiography is stressed, studies of other regions including the upper airway, abdomen, skull, and extremities are discussed. A brief consideration of the expanding role of new modality imaging (i.e., ultrasound, CT) is also included. Multiple illustrative examples of common and uncommon problems are shown.