An RF antenna arrangement of a combined MR/PET system is disclosed. In at least one embodiment, the RF antenna arrangement includes a first part installed in the examination tunnel in a fashion fixed to the system such that it is arranged underneath the couch board when the latter is introduced, and a second part, which can be placed onto the couch board and be introduced into and withdrawn from the examination tunnel together with the couch board. In at least one embodiment, the second part is of dimensionally stable design and has a clear cross section that is adapted to the object to be examined. Consequently, the time outlay for applying the RF antenna is reduced, and the fixed position of the RF antenna enables a correction of the attenuation of gamma rays. Furthermore, a number of second parts having various diameters can be provided.