The role of 18-fluorodeoxyglucose positron emission tomography (FDG-PET) in the diagnosis and monitoring of nonseminomatous germ cell tumours is currently unclear. Clinical studies have suggested that FDG-PET has relatively low sensitivity and specificity in the setting of initial staging and viability assessment of post-chemotherapy residual lesions. On the other hand, FDG-PET provides potentially useful information in patients with elevated tumour markers and/or multiple residual lesions with limited resectability. Other possible indications of FDG-PET are the early assessment of tumour chemosensitivity and the diagnosis of inflammatory treatment complications.