Medical examination or treatment apparatus, in particular X-ray or CT apparatus, comprising a controlling system controlling the operation of one or more apparatus elements, and at least one mobile operating element which is assigned to the control-ling system and which communicates wirelessly with the control-ling system for operating the examination or treatment apparatus for the transmission of operating signals, there being pro-vided at least one device which operates in a direction-selective and/or frequency-selective manner to modify the operating signals transmitted by the operating element such that a controlling system of examination or treatment apparatus disposed adjacent the examination or treatment apparatus to be intentionally operated is not activated by the modified operating signals or there being provided on the examination or treatment apparatus assigned to the operating element at least one acoustic and/or visual signal transmitter which is actuated when an operating signal is generated by the assigned operating element.