Applicability of the macro-scale elastic contact theories for the prediction of the collision dynamics involving nano-sized particles is examined. Essential parameters controlling the nano-scale collision are found by continuum-based Hertz (Hertz, 1896) and the JKR (Johnson et al., 1971) theories. Collision parameters of Lennard-Jones particles comprised of 2899 and 17,789 molecules onto a rigid flat surface are numerically obtained by a molecular dynamics simulation (MDS) method. MDS results validate the theories in terms of elastic limit velocity, the maximum compression force and the maximum radius of contact area. The elastic limit velocity of the nano-sized particles is accurately predicted by imposing the macro-scale elastic limit criterion. For the maximum compression force acting on the colliding nano-particle, Hertz impact theory shows good agreement with MDS result in both elastic and inelastic collision regimes. The theories incorporated with the correction factor for conforming contact accurately predicted the contact radius. Both theories are valid within the limit of the elastic collision. (C) 2012 Elsevier Ltd. All rights reserved.