The surface profile and the corresponding power spectral density function achieved by optical or mechanical profilometry operating in xz domain are always affected by probe dimensions and data digitization of the instruments. For mechanical profilometers there are typical changes in surface topography caused by system parameters like stylus radius, data digitalization and filtering. In this presentation the dependence of surface topography and statistical surface parameters on tip radius and data digitization is investigated by using a new numerical simulation model. In contrast to existing models the simulation algorithm presented in this paper determines the surface profile convoluted with the probe profile for any selection of surface and probe. For a sinusoidal and a fractal-like surface the distortion of the real profile by the probe geometry and the data digitalization is investigated and statistical surface parameters like root- mean-square-roughness Rq and correlation length lc are calculated. The statistical surface data achieved from the simulation procedure are compared with experimental data measured by a mechanical profile using different tips.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.