Uncertainties in the sub-nanometer range, the use of new materials, roughness, and the three-dimensional structures represent main challenges for the metrology of critical dimensions in nanostructures. In this paper, Monte Carlo modeling is used to investigate the correlation of the "true line edge roughness" of photoresist lines with the roughness rendered by Critical Dimension Scanning Electron Microscopy. Examples are presented, where realistic full-three dimensional photoresist structures in the nanometer range are generated by TCAD process simulation. (C) 2015 Elsevier Ltd. All rights reserved.