[en] The diffuse x-ray scattering from a single buried layer of quantum dots has been observed and interpreted to estimate the composition and shape of the dots. The diffuse scattering is measured on a modified laboratory diffractometer in very high-resolution mode, using the in-plane scattering geometry. The resultant reciprocal space maps were interpreted based on the distorted Born wave approximation. In-plane scattering removes all the influences except those associated with lateral inhomogeneities, i.e. the strain fields of the dots. This sample was also analysed by transmission electron microscopy, to extract the shape and by energy dispersive x-ray analysis to determine the composition. Despite the very different averaging volumes of the two approaches the results are in general agreement and suggest that this x-ray scattering method for this extreme case (very weak scattering from a single layer of dots) gives a useful estimate of the composition and shape of these structures