Objective: To analyse diagnostic efficiency of 18F-fluorodeoxyglucose (FDG)coincidence in detecting malignancy and compared with 99mTc-methylene diphosphonic acid 99mTc-methylene diphosphonate (MDP) bone scan.Methods: Clinically determine with malignancy 71 patients, male 45 cases, female 26 cases,mean age (59.2±15.4) years of age.71 patients underwent 99mTc-MDp(99mTc-Methylene diphosphonate) whole body bone imaging and 18F-FDG early or late within three weeks.Combine operation,puncture pathology, other image and follow-up,etc,integration analyse.Results: ①71 patients,include primary, metastasis and benign lesions in 350.Two methods all identified 81.7%(286/350) lesions, thereinto 18F-FDGidentified 142 lesions 40.6%(142/350) ,99mTc-MDP identified 209 lesions 59.7%(209/350).Both all identified 65 lesions 18.6 %(65/350),and differences between was 99mTc-MDP identified bone metastases and 18F-FDG didnt 144 lesions 41.1% (144/350).Statistical analysis the differences (X2=24.89; 216.64, P<0.01).②coincidence scan range of 209 bone metastases, the metastases found in the two imaging type (bone type, osteolytic, mixed type) were significantly different (X2=2.89~20.78, P<0.05~0.01).②The method that the number of cases of bone metastasis were 22.5%(16/71) and 59.2%(42/71)patients, a difference significant (X2=18.22, P<0.01).④The sensitivity, specificity, diagnostic accuracy, fake positive rate 、 fake negative rate, positive and negative predicting rate for detecting bone metastases was 84.4%,66.7%,81.6%,33.3%,15.6%,93.1% and 44.4% respectively with 18F-FDG, and was 71.9%,66.7%,71.1%,33.3%,28.1%,92.0% and 30.8% respectively with 99mTc-MDP.Conclusions: Detecting malignancy in the sensitivity, diagnostic accuracy, 18F-FDG is better than 99mTc-MDP in this group.But the later is predominance for fake negative rate, Combinewith them can be complementarity each other.Advance diagnostic efficiency.