The most recent multimodality technique, the hybrid positron emission tomography/magnetic resonance imaging (PET/MRI) combines two very different technologies, which is a great result of human creativity. The combined PET/MRI has significant potentials in clinical oncology providing new perspectives of functional and anatomical information. PET/MRI offers simultaneous measurements of multifunctional data such as PET mapping by different specific tracers or MRI morphologic, MR molecular (MR spectroscopy, MRS), or MR functional (fMR) information of a living system.