Left ventricular assist device implantation is an important therapeutic option for children with end-stage heart failure. However, device-related complications such as infection may occur while the patient is supported. Device-associated infection can be life-threatening, and early detection is critical. F-fluorodeoxyglucose positron emission tomography and CT is a highly sensitive imaging modality for the detection of an inflammatory response and is useful to evaluate the response to antibiotic therapy. We present two case reports of a left ventricular assist device-associated infection detected by F-fluorodeoxyglucose positron emission tomography and CT in children.