Strain relaxation has been studied for the 10‐period quantum well (QW) heterostructures grown by MOVPE, In0.16Ga0.84N/GaN and In0.2Ga0.8N/GaN, both emitting with high efficiency in the blue and green regions, respectively. Additionally, a set of high‐In content InGaN/GaN QW structures, where growth parameters were kept constant but QW numbers varied between 1 and 10, were also analysed by TEM, XRD and PL. For the highly‐efficient green and the set of variable QW samples, TEM structural studies identified large well‐width fluctuations and misfit dislocations that thread into the sample surface and are generated in the quantum well stack. This contrasts with similar observations of blue‐emitting MQWs where misfit dislocations are not seen. PL measurements have been carried out for the In‐rich QW series and did not reveal a greater degradation of the optical properties with increasing numbers of quantum wells in the stack. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)