Purpose We aim to compare FDG-PET/CT and cross-sectional imaging (contrastenhanced CT/MRI) diagnostic abilities in detecting recurrence/progression of pancreaticobiliary system tumors and to reveal the clinical impact of integrated FDGPET/CT to CT/MRI on patient management. Materials and Methods FDG-PET/CT and CT/MRI scans of 70 patients from initiation of treatment until proven recurrence/progression were retrospectively evaluated. FDGPET/CT and contrast-enhanced CT/MRI accuracy, sensitivity, specificity, PPV and NPV are compared in terms of overall recurrence/progression diagnosis and sitespecific concern; local disease, local lymph node, and distant organ metastasis. The impact of integrated FDG-PET/CT on patient management is scrutinized. Results CT/MRI has higher sensitivity than FDG-PET/CT in detecting loco-regional involvement (90% vs 76.7% P : 0.152), local lymph node metastasis (88.9% vs 77.8%, P : 0.380) and distant organ metastasis (96.5% vs 80.7%; P : 0.006) in tumor recurrence/progression. In overall diagnosis, CT/MRI is more sensitive and accurate but less specific than FDG-PET/CT (92.3% vs 87.7%; 87.1% vs 84.2%; 40% vs 20%, respectively). In 8% (6/70) of patients FDG-PET/CT had a major impact on patient management. Conclusion FDG-PET/CT and cross-sectional imaging have different advantages and shortcomings. In recurrence/progression, recognition of early changes is more feasible by CT/MRI. However, inconsistency of morphologic and metabolic findings is important reason of cross-sectional imaging failure. FDG-PET/CT is superior in showing extraabdominal metastases, but missing small-volume lesions and misinterpreting inflammatory changes are still a problem lowering its sensitivity. Nevertheless FDGPET/CT is good option for guiding undetermined imaging findings or clinic-radiologic mismatch.