Abstract: Multimodality imaging with PET-CTand SPECT-CT has become commonplace in clinical practice and in preclinical and basic biomedical research.Although PET-CT is already an established clinical tool it still bears some limitations.To overcome these limitations, recent research concentrates on the combination of PET and MRI into one single machine.Combined PET-MRI allows for multi-parametric imaging and reveals one or more functional processes simultaneously along with high-resolution morphology.Especially in small-animal research, where high soft tissue contrast is required, andthescantimeaswellasradiation dose are critical factors, the combination of PET and MRI would be beneficial compared with PET-CT.