The purpose of this study was to evaluate the usefulness of positron emission tomography with 18F-2-deoxyglucose (FDG-PET) for the detection of malignant bone metastases, and to compare FDG-PET results with conventional technetium-99m methylene diophosphate (Tc-99m MDP) bone scan findings. Twenty-four patients (10 females, 14 males, ages: 39-71 years) with biopsy-proven malignancy and suspected bone metastases, underwent whole body FDG-PET and bone scan to detect bone metastases. Bone metastases were established in 39 discordant bone lesions by histopathological examination of biopsy samples, MRI/CT, and follow-up bone scan/FDG-PET findings showing progressively and extensively widespread bone lesions. A total of 98 bone lesions found on either FDG-PET or bone scan were evaluated For 39 bone lesions with discordant findings between FDG-PET and bone scan, histopathological examination, MRI/CT and follow-up bone scan/FDG-PET findings revealed 8 metastatic and 0 benign bone lesions with positive FDG-PET findings, not detected on bone scan. Eleven metastatic and 20 benign bone lesions with positive bone scan findings were not detected on FDG-PET. FDG-PET has a better specificity, but a lower sensitivity for detecting malignant bone metastases when compared with bone scan.