Simultaneous PET/MRI was introduced into the commercial market only a few years ago, and its availability is currently gaining momentum with the introduction of a second-generation PET/MRI system from an additional vendor. Furthermore, there is still an increasing interest in its potential in clinical and research applications. Despite very early technical infancy problems, which meanwhile have been solved, there are still different limitations that have to be worked around in daily routine responsibly by the physicists and physicians. This article gives an overview over the most common technical, logistical, and clinical limitations; artifacts; and pitfalls, without any claim for completeness. The readers will not only learn the background of the limitation but also partly learn about possible solutions. At the end of each paragraph, the readers will find a short summary for an easier overview of the topics discussed.