Self-organized, buried InAs quantum dots covered by an AlAs diffusion barrier were investigated under UHV conditions using grazing incidence X-ray diffraction. The experimental data is compared to the simulated results obtained by Finite Element Method and Distorted Wave Born Approximation. We have found that the simulated data could be compared to the experimental one only after convolution by the resolution element which can be estimated from the experiment. By adjusting the simulation parameters we were able to find good agreement between the simulated and the measured data.