Abstract: Multimodality imaging, specifically PET-CT, brought a new perspective into the fields of clinical imaging.Clinical cases have shown that PET-CT has great value in clinical diagnosis and experimental reaserch.But PET-CT still bears some limitations.A major drawback is that CT provides only limited soft tissue contrast and exposes the patient to a significant radiation dose.MRI overcome these limitations, it has excellent soft tissue contrast, high temporal and spatial resolution and no radiation damage.Additionally, since MRI provides also functional information, PET-MRI will show a new direction of multimodality imaging in the future.