We report on the growth and properties of two types of AlGaN/AlN nanostructures: Stranski-Krastanow quantum dots (SK-QDs) and nanodisks (NDs) created by nanowire heterostructuring. In both cases, the emission wavelength can be tuned in the range of 240-350 nm at room temperature by varying the flux ratio and the nominal amount of AlGaN in the nanostructures. The efficient carrier confinement in these nanostructures leads to an internal quantum efficiency around 0.5. However, the emission spectra of AlGaN/AlN NDs show broader linewidth than those of SK-QDs, which is attributed to inhomogeneities in height and in chemical composition. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)