The Large Angle Convergent Beam Electron Diffraction (LACBED) technique has been applied to determination of the tetragonal mismatch in coherent Si/Si1-xGex/Si heterostructures. Two-dimensional (2D) dynamical simulation of the LACBED patterns has been performed and compared with the corresponding experimental ones. A good agreement is found in the whole simulated area, particularly as regards the splitting of the Bragg contours, due to the strain field present in the TEM cross-sections.