10589 Background: We evaluated the clinical utility of 18F-sodium fluoride PET/CT bone scan (18F-NaF) in the detection of bone metastases in patients (pts) with prostate cancer in comparison with Technetium-99m MDP bone scan (TcBS). Methods: In a prospective study, from October 2010-December 2011, 30 prostate cancer pts (ages 51-79), 21 with known bone metastases and 9 without known bone metastases, had18F-NaF and a TcBS performed. Abnormal foci of uptake on both TcBS and 18F-NaFwere classified as benign, malignant or indeterminate. Benign lesions included uptake in the joints and linear uptake at the endplates of the vertebral bodies consistent with degenerative changes. Malignant uptake on 18F-NaF scans was confirmed by characteristic osteoblastic features on CT. All TcBS and 18F-NaF were reviewed by an experienced nuclear medicine physician. For the patient-based analysis, scan results were categorized as positive (POS) = any malignant lesion; indeterminate (IND) = not distinctly malignant or benign; negative (NEG) = benign lesions only. Results: In the lesion-based analysis, 21 of 30 (70%) pts had more malignant lesions identified on 18F-NaF than on TcBS. The mean number of additional malignant lesions per patient on 18F-NaF vs TcBS was 4. Eight of the 30 pts had same number of malignant lesions identified in both studies. One of 30 pts had one less malignant lesion identified on 18F-NaF than on TcBS. CT correlation by 18F-NaF PET/CT of this particular lesion did not confirm osteoblastic feature. Malignant lesion distribution on 18F-NaF included: spine (28%), thorax (26%), pelvis (24%), long bones (13%) and skull (10%). In the patient-based analysis, 24 pts (80%) were POS by 18F-NaF, of whom 14 pts were POS, 8 were IND, and 2 were NEG by corresponding TcBS; in the 4 pts with NEG 18F-NaF, zero were POS, 2 were IND and 2 were NEG by corresponding TcBS. Conclusions: 18F-NaF identified more malignant lesions than TcBS. 18F-NaF may also add useful information in the management of advanced prostate cancer pts with and without known bone metastases.