Abstract: Langerhans cell histiocytosis (LCH), formerly known as histiocytosis X, is a group of monoclone derived dendritic cell proliferative diseases. This histiocyte exhibits the characteristics of Langerhans cells, which primarily include bone destruction, benign focal histiocytosis, and eosinophil infiltration. The cause of the disease remains unknown at present. LCH can occur at any age, but more than 50% of the cases were reported in children aged 1−15 years old and can involve multiple systems and organs. The onset of the disease varies. Severe cases can involve extensive organ infiltration with fever and body weight reduction. LCH with simple bone destruction is easily misdiagnosed, and thus, the author selected two LCH cases through their ¹⁸F-FDG PET/CT imaging features and clinical data for differential diagnosis and then summarized the diagnosis idea to improve imaging diagnostic accuracy.