Infantile myofibromatosis, a rare, nonmalignant disease seen almost exclusively in the pediatric population, can involve skin, muscle, soft tissues, bone, or viscera in either solitary or multicentric pattern. Although nonmalignant, visceral involvement in infantile myofibromatosis is a key prognostic indicator, which is associated with mortality in 75% of patients. Those with pulmonary involvement have a particularly poor outcome. This case illustrates the diagnostic utility of F-FDG PET/CT in defining disease extent in this unusual entity and compares it to other commonly used imaging modalities.