Integrated whole‐body PET/MR hybrid imaging combines excellent soft tissue contrast and various functional imaging parameters provided by MR with high sensitivity and quantification of radiotracer metabolism provided by positron emission tomography (PET). While clinical evaluation now is under way, integrated PET/MR demands for new technologies and innovative solutions, currently subject to interdisciplinary research. Attenuation correction of human soft tissues and of hardware components has to be MR‐based to maintain quantification of PET imaging because computed tomography (CT) attenuation information is missing. This brings up the question of how to provide bone information with MR imaging. The limited field‐of‐view in MR imaging leads to truncations in body imaging and MR‐based attenuation correction. Another research field is the implementation of motion correction technologies to correct for breathing and cardiac motion in view of the relatively long PET data acquisition times. Initial clinical applications of integrated PET/MR in oncology, neurology, pediatric oncology, and cardiovascular disease are highlighted. The hybrid imaging workflow here has to be tailored to the clinical indication to maximize diagnostic information while minimizing acquisition time. PET/MR introduces new artifacts that need special observation and innovative solutions for correction. Finally, the rising need for appropriate phantoms and standardization efforts in PET/MR hybrid imaging is discussed. J. Magn. Reson. Imaging 2014;39:243–258. © 2013 Wiley Periodicals, Inc.