We study the cathodoluminescence (CL) and the photoluminescence (PL) properties of InxGa(1-x)N/GaN quantum disks (QDisks) included in nanowires obtained by selective area sublimation from an InxGa(1-x)N/GaN multiple quantum well using an in situ SixNy nanomasking performed in a molecular beam epitaxy reactor. The NW density can be adjusted as a function of the SixNy coverage. The mean NW diameter is found almost constant for NW density varying by two orders of magnitude. The light emission from the InxGa(1-x)N/GaN QDisks is blue-shifted compared to the quantum wells. The origin of this shift is discussed in terms of strain and lateral confinement effects in the QDisks. The CL and PL spectra reveal strongly reduced peak linewidths for experiments conducted on a few or single objects isolated by using sub-micrometer apertures in a metallic mask. (C) 2017 Elsevier B.V. All rights reserved.