Abstract: The invention relates to a method for registering structures on microlithographic masks comprising the comparison of a recorded measurement image of a mask and the target design underlying the mask, wherein the target design underlying the mask is converted into a simulated reference image that is directly comparable with the measurement image with the aid of an optical simulation, wherein the optical simulation is fully automatically differentiable in such a manner that a metric that is determined from the recorded measurement image and the reference image simulated in the forward mode and represents the differences allows in the backward mode a representation of the actual design of the mask that is directly comparable with the target design for the purpose of determining possible defects of the mask. The invention furthermore relates to a corresponding computer program product and to the use of the above method in the course of a microlithographic process.