A combiner/splitter device (100) comprises two transmission lines (23, 24), wound to form a helical coil (55), this helical coil being bent to a toroidal shape. Furthermore, a capacitor (51) is provided, connected in parallel with the two outer conductors (25, 26) of the two transmission lines (23, 24). The combination of the wound transmission lines and said capacitor forms a parallel resonator (56). The combiner/splitter device is suitable for use in a magnetic resonance imaging (MRI) system to combine the output signals of a receiver coil system and/or to split the input signal of a transmission coil system used in the MRI system.