A combined positron emission tomography/magnetic resonance imaging apparatus for imaging organs of an examination object in an examination space is disclosed, including a positron emission tomography apparatus having at least one radiation detector, and a magnetic resonance imaging apparatus having at least one gradient coil and a radio-frequency antenna device. In order to prevent mechanical oscillations being induced in the PET gantry by the gradient coil, at least one embodiment of the combined position emission tomography/magnetic resonance imaging apparatus is developed further in that a first molding is provided, whose surface coincides with the inner shell of the at least one gradient coil, and a second molding is provided, whose surface coincides with the outer shell of the radiation detector, the distance between the two shells being virtually constant over the circumference of the shells, and a vacuum seal being arranged in each case along at least a first and a second circumferential line such that a closed cavity is formed between the vacuum seals.