Density functional theory (DFT) calculations have been performed to predict the reactivity pattern governing the nucleophilic, electrophilic and radical attacks on the external surface of open and capped (5,5) armchair single-walled carbon nanotubes (SWCNTs). The DFT-based local reactivity descriptors, viz, Fukui function, local softness, relative electrophilicity, relative nucleophilicity and dual reactivity descriptor, have been examined for predicting the reactivity of different carbon atom sites of the considered SWCNTs. The predictions of regioselectivity using relative electrophilicity, relative nucleophilicity and dual reactivity descriptors have been verified by reaction energies calculated for model systems at the M06-2X/6-31G(d) level. (C) 2012 Elsevier B. V. All rights reserved.