Critical dimension metrology relies on the analysis of electron‐beam signal profiles from structures of arbitrary size and shape. Conventional modeling techniques for simulating such profiles use Monte Carlo techniques which, while very accurate, require considerable computing time since any change in any parameter necessitates a complete new calculation. This paper describes an alternative approach in which a Monte Carlo simulation is used to derive the coefficients of a diffusion matrix. From this matrix the backscattering and secondary electron profiles from a surface of given geometry can be found by simple summation, and the results of a change in the geometry can be determined immediately without the need for further computation. The predictions of this method are in excellent agreement with those of the conventional approach.