Many groups attempt to optimize imaging protocols on PET/MR imaging systems. Although research protocols may take as long as 60-90 min, much more efficient clinical workflows are needed to achieve cost-effective examination times of less than 1 h. Considering these difficulties, simultaneous PET/MR imaging is an intriguing research tool, but its clinical applications are uncertain or just beginning to emerge. However, unlike PET/CT, in which the options for various CT protocols are limited, the MR imaging portion of PET/MR imaging can be extended arbitrarily depending on the MR pulse sequences chosen. For PET/MR imaging to be complementary, feasible, and somewhat competitive with PET/CT, image acquisition times should ideally be limited to 30 min. The purposes of this article are to help the reader to understand the critical workflow issues in simultaneous PET/MR imaging in comparison with sequential PET/MR imaging and to learn how to optimize an imaging examination. Current knowledge toward this goal is summarized.