Traditional UV/optical surveys to identify (radio-quiet) quasi-stellar objects (QSOs) are strongly biased against dusty objects. Investigation of infrared-selected galaxies has revealed the presence of QSOs with properties indistinguishable from the UV/optically selected QSOs, except that they are obscured along our line of sight by dust. Many are dominated by Type-2 (narrow-lined) spectra in the optical, but show Type-1 (broad lined) spectra in scattered light. The inferred space densities of these Type-2 QSOs imply that dusty QSOs contribute significantly to the infrared background and the total energy budget of the universe.