The role of diagnostic imaging in pediatric intensive care units (PICU) includes primary diagnosis, monitoring of the patient's progress, and the assessment of interventional procedures. Images should be acquired in the PICU, not only to minimize the time interval between image acquisition and image interpretation but also in order to avoid unnecessary and maybe harmful transportation of the patient. Portable, optimized equipment is warranted. Most images are acquired as conventional X-ray examinations. Thorough consideration of radiation protection based on optimized equipment also includes the protection of relatives and other children in the PICU room. Ultrasound is an expanding imaging modality adjunct or as alternative to conventional X-ray examinations, which allows the generation of functional information (color-coded duplex, elastography). Fluoroscopy, computed tomography, and magnetic resonance imaging are available as advanced diagnostic modalities in special circumstances, but require transportation of the patient.