Photoluminescence of HgCdTe epitaxial films and nanostructures and electroluminescence of InAs(Sb,P) light-emitting diode (LED) nanoheterostructures were studied. For HgCdTe-based structures, the presence of compositional fluctuations, which localized charge carriers, was established. A model, which described the effect of the fluctuations on the rate of the radiative recombination, the shape of luminescence spectra and the position of their peaks, was shown to describe experimental photoluminescence data quite reasonably. For InAs(Sb,P) LED nanoheterostructures, at low temperatures (4.2–100 K) stimulated emission was observed. This effect disappeared with the temperature increasing due to the resonant ‘switch-on’ of the Auger process involving transition of a hole to the spin-orbit-splitted band. Influence of other Auger processes on the emissive properties of the nanoheterostructures was also observed. Prospects of employing II–VI and III–V nanostructures in light-emitting devices operating in the mid-infrared part of the spectrum are discussed.