FDG PET/CT whole-body imaging has higher sensitivity, specificity and accuracy as compared to CT in detection of metastatic spread and follows up after treatment. The aim of this study: to assess of the impact of PET/CT in patients with metastatic breast cancer and monitoring the therapy response in relation to different molecular subtypes. Material and Methods: The study included 40 patients classified into 4 molecular subtypes; Luminal A like subtype (13 patients), Luminal B+ subtype (15 patients), Luminal B- subtype (4 patients) and Basal like subtype (8 patients). All patients with possible metastatic breast cancer performed PET-CT before treatment, while 34 patients perform PET-CT after the end oftherapy. Results: on lesion based analysis the total numbers of metastatic lesions in CT and bone scan were 120 lesions (49 in LNs, 24 in lung, 8 in liver; while 39 in bone). Metastatic lesions in PET/CT were 76 lesions (46 in LNs, 22 in lung and 8 in liver and 22 in bone). During follow up after therapy, the majority of luminal A group showed complete response to therapy during follow up PET/CT scan. Also, luminal B+ subgroup showed partial response. While most of basal-like subgroup showed progressive disease. Conclusion: PET/CT can detect metastatic spread in breast cancer and monitor therapy response in relation to different molecular subtypes. The mean SUV max showed relation to the different molecular subtypes.