The coordinated application of low-pressure mass spectrometric and high-pressure radiolytic techniques, supported by ab initio calculations, results ideal for investigating structural and mechanistic problems in the gas-phase ion chemistry of organometallic compounds. The major advantages of this multipronged approach, i.e. the wide pressure range and the positive structural and stereochemical characterization of the charged intermediates, are demonstrated by the results of recent applications. The examples discussed, dealing with the reactivity of gaseous germylenium and silylenium ions as well as the behavior of Si- containing gaseous carbocations, illustrate the relevance of these studies, which often represent, inter alia, the only experimental means to evaluate the intrinsic properties of these otherwise highly elusive species in condensed phase.