Reactive molecules bind to the non-equivalent bonds of a nanotube differently. The site-preference for binding an interior C-1-C-59 fullerene to a (10, 10) nanotube is significantly different from the case of the interior CH2 molecule. Nanotube confinement influences the site-preferences of the endohedral covalent-bond formation through the steric hindrances between the C-1-C-59 fullerene and the nanotube, while there is no steric hindrance in the CH2 case. Despite the different confinement of a guest inside the nanotube, the power of the C-1-C-59 molecule to modify the nanotube structure locally, creating butadiene-like and quinonoid-like patterns, is comparable to that of the CH2 molecule. (C) 2007 Elsevier B.V. All rights reserved.