Abstract: The authors reported a case of giant multilocular prostatic cystadenoma (PC) with ¹⁸F-fluorodeoxyglucose (FDG) PET/CT imaging, and the imaging characteristics and differential diagnosis of the disease were analyzed. ¹⁸F-FDG PET/CT can not only locate the lesion and determine the relationship between it and the surrounding tissues, but also identify benign and malignant according to the degree of radioactive uptake of the tumor, thus providing sufficient evidence for clinical diagnosis. Since PC is rare in clinical practice, and there is no report on the application of ¹⁸F-FDG PET/CT for diagnosis, the author analyzed the ¹⁸F-FDG PET/CT imaging characteristics of this case, aiming to improve the understanding of the disease and avoid misdiagnosis.