Background Years ago the utility of of18F-fluorodeoxyglucose-positron emission tomography/computerized tomography (18FDG-PET/CT) in differentiated thyroid cancer was confined mainly to cases with elevated serum thyroglobulin and negative 131I whole body scan. In this study, we try to assess the diagnostic performance of 18FDG-PET/CT in recurrent differentiated thyroid cancer patients with positive 131I whole body scan and in addition to evaluate the impact of 18FDG-PET/CT on the treatment strategy. Results The 18FDG PET/CT detected tumor recurrence in 35 (81.3%) patients most of them (91.4%) were in stage IV, while the rest 8.5% was in stage III. No recurrence was detected among patients in stage II and III by 18FDG PET/CT. Regarding lesion-based analysis, sensitivity of 18FDG-PET/CT was superior to that of 131I post-therapeutic whole body scan (TxWBS) (78.2% vs. 69.4%, respectively), while both modalities had the same specificity (50%). 18FDG-PET/CT changed the treatment plan in 18 (41.6%) patients. Conclusion 18FDG-PET/CT may be complementary to 131ITxWBS in high-risk DTC with impact on treatment strategy.