Self-assembly of diblock copolymers (BCP) into periodic arrays is a promising route to generate templates for the fabrication of nanoscopic elements, when one block is selectively removed. In cylindrical morphology polystyrene-blockpoly(methyl methacrylate) (PS-b-PMMA) copolymer (BCP) films, the efficiency of different processes for removing the PMMA from cylinders is studied using grazing incidence small angle X-ray scattering (GISAXS), x-ray reflectivity and critical dimension scanning electron microscopy. The detailed analysis of the GISAXS patterns leads to the determination of the depth of cylindrical holes left by removal of the PMMA. It is found that the combination of a preliminary UV exposure followed by a wet treatment allows to remove totally the PMMA blocks. Furthermore, the optimization of both UV exposition time and solvent allows to preserve the PS matrix and interestingly for nanolithographic applications to decrease the process costs. (C) 2016 Wiley Periodicals, Inc.