Sideband optical-optical double resonance Zeeman spectroscopy is applied here to studies of the electronic spectrum of gas-phase PtH. Even though each rotational transition is a composite line with closely spaced isotope and hyperfine structure, the sub-Doppler Zeeman spectrum of each feature has been recorded and analyzed using a systematic, quasi-two-dimensional approach. Sub-Doppler radio frequency magnetic resonances, in addition to their diagnostic power to assist rotational and electronic assignment, can also be used to detect selectively other transitions with the same Zeeman properties; if a fixed magnetic field is applied and the sub-Doppler signal recorded as the laser is scanned, spectral features which share the common Zeeman splitting in either the lower or upper state can be detected. Several examples illustrating the selectivity of this scheme are given. (C) 1997 American Institute of Physics.