Objective:To investigate the value of 18F-fluorodeoxyglucose(FDG) dual-head coincidence imaging in the diagnosis of recurrent and metastatic differentiated thyroid carcinoma. Methods:Twenty-eight patients with differentiated thyroid carcinoma after post-therapy and radiotherapy with 131I were studied with 18F-FDG dual-head coincidence imaging and 131I whole body imaging. The results were analyzed by calculating its sensitivity, specificity,accuracy,positive predicative value(PPV) and negative predicative value(NPV), compared with thyroglobulin detected. Results:There were 8 true positive cases,13 true negative cases,1 false positive case,6 false negative cases in 28 postoperative patients detected by 18F-FDG dual-head coincidence imaging. The sensitivity, specificity, accuracy, positive predicative value and negative predicative value were 57.1%,92.8%,75.0%,88.9% and 68.4%,respectively. while levels of Tg were more than ≥10 ng/ml,the sensitivity of detecting recurrent carcinoma were higher in cervical lymph lode and bone by 18F-FDG dual-head coincidence imaging. Conclusions:18F-FDG dual-head coincidence imaging holds promising clinical value for diagnosis of patients with differentiated thyroid carcinoma after resection and radiotherapy with 131I, especially for the domestic widespread application of SPECT DHC instrument, which can lower the expense of detection practically.