The convolutional multiple whole profile fitting method of X-ray line profile analysis using synchrotron radiation allows the experimental determination of dislocation densities separately for different Burgers vectors up to a high degree of deformation. Its reliability for Mg–Zn–Y alloys, in terms of the dislocation activity during tensile deformation, has been successfully verified by combined analysis with electron backscatter diffraction investigation and visco-plastic self-consistent simulation.