This paper presents a detailed study on computer simulations of resist profiles obtained in x‐ray lithography for exposures made either with synchrotron radiation or with an Al–Kα source. It is assumed, for purposes of the calculations, that the vacuum windows consist of kapton and that silicon is used as the mask material. The influence of edge shape and mask absorber thickness upon the resist structure is of special interest. The other parameters affecting resist profiles, such as Fresnel diffraction (especially in the case of semitransparent absorbers) and photoelectron range, are taken into consideration. In the case of the x‐ray tube, the penumbral blur caused by the finite dimensions of the source spot leads to an additional deterioration of the edge sharpness. For the calculations, the intensity distribution over the spot area was assumed to be uniform (with Gaussian‐shaped edges). The influence of the photoelectron range upon the resist profiles is calculated, using the simple depth‐dose relationship of Gruen. The calculated resist profiles are compared with typical experimental results.