Coronary artery diseases represent a significant cause of death worldwide. In fact, their occlusion can cause lack of oxygen to the heart tissue, leading to heart failure or heart attack. Coronary artery bypass grafting is a surgical procedure to restore a proper blood supply. In this context, Computational Fluid Dynamics (CFD) can be a significant tool to improve coronary artery bypass grafts and to avoid unfavorable flow conditions in the region of the anastomosis, which can be associated with the failure of the surgical procedure. In this work the development of a Reduced Order Model (ROM) for the investigation of hemodynamics in a patient-specific configuration of coronary artery bypass graft is proposed.