Combined positron emission tomography and magnetic resonance imaging (PET/MRI) is emerging as a powerful technique in clinical applications including oncology, neurology, and cardiology. In this review, we outline recent advances in the field, with particular focus on the study of neurodegenerative diseases, epilepsy, cardiac disorders, and oncology. We also highlight recent technical improvements in PET/MRI, with particular attention to attenuation correction and the integration with advanced MRI modalities including arterial spin labeling, fMRI, and hyperpolarized 13 C magnetic resonance spectroscopy.