The invention relates to an open magnetic resonance imaging (MRI) magnet system (1) for use in a medical imaging system. The open MRI magnet system has two main coil units which are accomodated, at some distance from each other, in a first housing (2) and in a second housing (3), respectively. Between the two housings, an imaging volume (6) is present wherein a patient to be examined is placed. A gradient coil unit (9, 10) facing the imaging volume is present near a side of each of the two housings. Functional connections of the gradient coil units (9, 10), such as electrical power supply lines (13, 14) and cooling channels (15, 16) are provided in a central passage (4, 5) which is present in each of the two housings. As a result, these functional connections do not reduce the space in the imaging volume available for the patient. The central passages and the electrical power supply lines provided therein are parallel to the direction of the main magnetic field of the open MRI magnet system, so that the Lorentz forces exerted on the power lines are limited.