I present preliminary results and discussion from a K-band imaging study of the host galaxies of samples of ULIRGs and IR-bright QSOs, designed to match in terms of their FIR luminosities and redshift distributions. Large K-band bulges are found to be present in all of the quasars, with the majority of the ULIRGs being best-fit by a disc. Despite the apparent difference, a significant overlap exists between the two populations in terms of their nuclear luminosity. A significant unresolved nuclear component is present in all of the objects, and this is found to correlate with the luminosity of the K-band host across the sample.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html