1. A method for determining a position of structures on a mask for microlithography, wherein the position determination is effected on a basis of a comparison of an aerial image, measured by a recording device, of a portion of the mask with an aerial image determined by simulation, the method comprising: measuring an aerial image of a portion of a mask for microlithography, the portion of the mask having structures; performing a plurality of simulations of aerial images of the portion of the mask based on different input parameters; and determining, using a computer, the position of the structures by carrying out a plurality of comparisons between the measured aerial image and the simulated aerial images, wherein the comparisons differ from one another with regard to the input parameters of each respective simulation; wherein varied input parameters of the simulation comprise at least one of mask parameters based on three-dimensional extent of the mask or optical parameters of an optical system for generating the measured aerial image in the recording device; said method further comprising the following steps: determining a set of input parameters for which an associated comparison of the plurality of comparisons yields the best correspondence; determining a further aerial image by simulation on a basis of said set of parameters; carrying out a comparison of this further simulated aerial image with the measured aerial image; and determining a positioning error of a structure of the mask on a basis of said comparison.