A combined positron emission tomography/magnetic resonance imaging apparatus, in a trailer housing is disclosed, for imaging organs of an examination object in an examination space. In at least one embodiment, the positron emission tomography/magnetic resonance imaging apparatus includes a positron emission tomography apparatus with at least one radiation detector and a magnetic resonance imaging apparatus with at least one main magnetic field coil for generating a main magnetic field, at least one gradient coil for generating a magnetic gradient field, and a radio-frequency antenna device for transmitting excitation pulses and receiving magnetic resonance signals from the examination space, the radiation detector and the at least one gradient coil being arranged coaxially and at substantially the same axial height. In order to create a mobile MRI/PET apparatus which is designed as compactly as possible and, firstly, satisfies the radiation protection requirements for protecting the surroundings of the measurement apparatus to the best possible extent and, secondly, excludes interfering environmental influences on the measurement apparatus, a shielding arrangement with at least one shielding element for attenuating the main magnetic field and the gradient field and also the annihilation radiation outside the trailer housing is provided in at least one embodiment.