We present a high momentum transfer (Q) X-ray scattering method to determine the thickness and indium composition of an InxGa1-xN well in InGaN/GaN multiple quantum wells. At high-Q, it is demonstrated that the scattering signal from InGaN well layers is separated from that of GaN barrier layers. The structure factor of the well layers is determined from the envelope of the superlattice reflections. The thickness and the indium composition of the well layer are obtained directly from the structure factor. We discuss the high-Q analysis in comparison with the analysis of low-Q data where the scattering from InGaN well and GaN barrier interferes strongly. (c) 2006 Elsevier B.V. All rights reserved.