Objective: the aim of this study was to compare the role of PET/CT & bone scintigraphy in detection of bone metastasis in patients with breast cancer. Patients and methods: The present study included 30 patients with breast cancer. Their ages ranged between 25years and 65 years with mean age of 45 years old. All patients were subjected to full history taking, clinical breast examination, histopathology investigation, 99mTc-MDP Whole body bone scan, whole body positron emission tomography / computed tomography (FDG- PET/CT). Results: on patient-based analysis in this study thirty patients were examined with bone scintigraphy and FDGPET/CT. only 24 (80%) were detected by FDG-PET/CT had metastasis compared by only 18 (60%) patients detected by bone scintigraphy. On lesion-based analysis in this study 71 lesions detected by FDG-PET/CT (positive 50 lesions (70.42%) - negative 21 lesions (29.58%), compared by 62 lesions detected by bone scintigraphy (positive 43 lesions (69.35%) – negative 19 lesions (30.65%). Conclusion: whole-body FDG-PET/CT is more sensitive and equally specific for the detection of bone metastases compared with bone scintigraphy. Both bone scintigraphy and FDG-PET/CT give false-positive results due to various common benign bone processes which are the most disadvantages of both modalities.