Various designs of positron emission tomography/magnetic resonance imaging (PET/MRI) systems have been recently introduced to clinical practice, which have overcome preexisting technical challenges concerning the fusion of PET and MRI systems. Although further improvements are still necessary especially for bony lesions, quantification using current MRI-based attenuation correction techniques has been shown to be comparable to that of PET/computed tomography (CT) systems. On the basis of the results of previous whole-body MRI studies, PET/MRI is expected to show even better performance than PET/CT in M-staging especially for brain and liver metastases. Another advantage of PET/MRI over PET/CT, in addition to good soft tissue contrast, is the potential reduction in radiation dose. The next important hurdle to overcome for its clinical application is the development of time-efficient protocols for lung cancer evaluation and interpretation of discordant results from both modalities. Multiparametric imaging through PET/MRI will help radiologists better understand tumor biology and better evaluate treatment response.