Abstract: Primary mediastinal neuroendocrine neoplasms (NEN) are relatively rare and highly heterogeneous tumors. Histopathological examination is the "gold standard" for their diagnosis. The authors report a case of primary mediastinal NEN in an elderly male patient, with findings from ¹⁸F-fluorodeoxyglucose PET/CT imaging. The characteristics of this disease are analyzed and discussed from multiple perspectives, including clinical presentation, pathology, imaging and differential diagnosis, and treatment, aiming to facilitate a more accurate diagnosis of this disease.