We focus on the problem of obtaining and characterizing the edge roughness of photoresist lines by analyzing top-down scanning electron microscope (SEM) images. An off-line image analysis algorithm detecting the line edge, and an edge roughness characterization scheme, based on scaling analysis, are briefly described. As a result, it is suggested that apart from the rms value of the edge (sigma), two more roughness parameters are needed: the roughness exponent α and the correlation length ζ. These characterize the spatial complexity of the edge and determine the dependence of sigma on the length of the measured edge. Completing our previous work on the dependencies of the roughness parameters (sigma,α,ζ) on various image analysis options, we examine the effect of the type of noise smoothing filter. Then, a comparative study of the roughness parameters of the left and right edges of resist lines is conducted, revealing that the sigma values of the right edges are larger than those of the left edges (due to an imperfect SEM beam alignment), whereas the roughness exponents and the correlation lengths do not show such a trend. Finally, the relation between line width roughness and line edge roughness is thoroughly investigated with interesting conclusions.