We investigate the noncovalent functionalization of metallic single-walled carbon nanotubes (SWCNT) (6,0) by 4,4'-methylene diphenyl diisocyanate (MDI) and toluene-2,4-diisocyanate (TDI) molecules using the density functional theory (DFT) method with van der Waals dispersion correction. The obtained local minima show the dependence between the molecular arrangement of the adsorbates on SWCNT surface and their binding energies. We analyze the interplay between the pi-pi stacking interactions and isocyanate functional groups. For the analysis of the changes in the electronic structure we calculate the density of states (DOS) and charge density plots. (C) 2014 Elsevier B.V. All rights reserved.