Objective: To investigate the value of 18F-FDG dual head coincidence imaging for diagnosis of nasopharyngeal carcinoma.Methods: A total of 45 patients with nasopharyngeal carcinoma (33 males, 12 females, average age 55.56±13.50y), who had 18F-FDG dual head coincidence imaging before treatment, were studied retrospectively.There were 34 patients with undifferentiated non-keratinizing carcinoma and 11 patients with differentiated non-keratinizing carcinoma.The pictures of SPECT/CT and MRI were analyzed with qualitative and semiquantitative analysis.The radioactivity of the reigons of the focuses was researched by qualitative analysis, statistical analysis of the T/NT of SPECT/CT (the radioactive ratio of focus to cerebellum, calculated by region of interest technique).The volum of the focus of nasopharyngeal carcinoma was recoreded by MRI.The positive rate of 18F-FDG dual head coincidence imaging and EB virus-related antibody were compared by x2 test.The correlation between T/NT and the volum of tumour was tested by Pearson correlation.The ROC curves of T/NT and the volum of tumour were established.The T/NT and the volum of tumour between different groups were compared, which were grouped by the nasal symptoms, the auditive symptoms, the symptoms of nervous system, with or without lymph node enlargement, clinical stages, T stages, pathological classification and the outcomes.Results: The positive rate of 18F-FDG dual head coincidence imaging was 97.78%, the positive rate of EB virus-related antibody was 95.56%, with no significant difference between the positive rate of 18F-FDG dual head coincidence imaging and that of EB virus-related antibody (x2=1.33,P>0.05).The T/NT and the volum of tumor were (2.439±1.119) and (7.311±8.280) cm3 respectively.There was positive correlation between the T/NT and the volum of tumour (t=0.463,P<0.05).The cut-off values of T/NT and the volum of tumour were 2.396 and 7.348 by ROC curves.There were no significant differences for the T/NT and the volum of tumor between the groups of clinical stages or the T stages (P>0.05).There were significant differences for T/NT between difference groups according to nasal symptoms, the symptoms of nervous system and pathological type(P<0.05), with a significant difference (P<0.05) for the volum of tumour for difference groups according to the symptoms of nervous system.The were no significant differences for the T/NT and the volum of tumor between the groups of the auditive symptoms,with or without lymph node enlargement and the outcomes (P>0.05).Conclusions: 18F-FDG dual head coincidence imaging is a feasible non-invasive technique for the early diagnosis of nasopharyngeal carcinoma.The cut-off value of T/NT is helpful for the early diagnosis and prediction of prognosis of nasopharyngeal carcinoma.