BACKGROUND: The various origins of obstructive jaundice make the diagnosis of the disease difficult. This study was undertaken to evaluate the role of F-18-FDG PET/CT in differentiating malignant from benign origins of obstructive jaundice and to quantify the added value of F-18-FDG PET/CT over conventional imaging (enhanced CT and/or MRI). METHODS: Eighty-five patients with obstructive jaundice who underwent F-18-FDG PET/CT within 2 weeks after enhanced CT and/or MRI were reviewed retrospectively. All F-18-FDG PET/CT images were independently evaluated by 2 nuclear medicine physicians who were unaware of other imaging data; differences were resolved by consensus of the physicians. All conventional imaging interpretations, according to the medical records, were reviewed by 2 radiologists to determine the potential value. Final diagnoses were based on histological or surgical findings. RESULTS: Sixty-six patients were diagnosed with malignancies, and 19 patients with benign lesions. The maximum standardized uptake values for malignant and benign lesions causing binary obstruction were 8.2 +/- 4.4 and 4.0 +/- 5.0, respectively (P<0.05). The sensitivity, specificity, and overall accuracy for differentiating malignant from benign origins with F-18-FDG PET/CT were 86.4% (57/66), 73.7% (14/19), and 83.5% (71/85), respectively. F-18-FDG PET/CT in conjunction with conventional imaging changed the sensitivity, specificity, and overall accuracy of conventional imaging alone from 75.8% (50/66) to 95.5% (63/66) (P<0.05), 68.4% (13/19) to 57.9% (11/19) (P>0.05), and 74.1% (63/85) to 87.1% (74/85) (P<0.05), respectively. CONCLUSIONS: F-18-FDG PET/CT is of great value in differentiating malignant from benign origins of obstructive jaundice and is a useful adjuvant to conventional imaging. F-18-FDG PET/CT should be recommended for further etiological clarification.