The aim of the study was to examine the effectiveness of fluorine-18 fluoro-2-deoxy-D-glucose positron emission tomography/computed tomography (18F-FDG PET/CT) versus bone scintigraphy (BS) in treatment response assessment of bone metastases in breast cancer.The medical records of breast cancer patients with metastatic bone disease were reviewed retrospectively in our hospital from the period of January 2003 until April 2014. We included in our study patients evaluated by BS and/or 18F-FDG-PET/CT. Group 1 included patients who underwent pre- and post-treatment BS. Group 2 included patients who underwent pre- and post-treatment 18F-FDG-PET/CT scans. Group 3 included patients who underwent pretreatment BS and post-treatment both modalities. Functional and structural bone changes were monitored on pre- and post-treatment scans.Group 1 included 71 patients, average age of 49.5 y (range 28-73 y). Post-treatment results were as follows: 34% stable disease, 43% progressed disease, 19% improved disease, 3% resolved disease, and 2% relapsed disease. Group 2 included 32 patients, average age 53.2 y (ranges between 37 and 78 y). Post-treatment results were as follows: 3% stable disease, 15% progressed disease, 15% improved disease, 53% resolved disease, and 14% relapsed disease. After treatment, the total symptomatic/imaging concordance rate was 51% in BS and 83% in 18F-FDG-PET/CT. Structurally, most patients with newly diagnosed metastatic bone disease had predominantly osteolytic lesions, which became mixed or osteoblastic after treatment as noted on CT images of responders. Group 3 included 8 patients, average age 48.9 y (ranges 32-64 y). Five patients had stable disease according to BS. 18F-FDG-PET/CT was concordant in 3/5 patients and discordant in 2/5 patients. Three patients had progressed disease on BS with concordant findings on 18F-FDG-PET/CT.18F-FDG-PET/CT was found a powerful tool in treatment response assessment of bone metastases in breast cancer and consistent with clinical status of the patients as it reflects tumor activity. BS is insufficient for response assessment of bone metastases as it reflects osteoblastic reaction of the bone against metastatic disease which increases as the disease responds to treatment.