The performance of a number of density functionals in describing intramolecular dispersion interaction has been assessed by studying the conformational energy differences between the all-gauche and all-trans conformers of large normal alkanes. The generalized energy-based fragmentation approach is applied to perform CCSD(T) or MP2 calculations for these large alkanes. The M06-2X functional is demonstrated to provide satisfactory descriptions. With an empirical dispersion correction, some functionals like wB97X and LC-wPBE can also show comparable performance as the M06-2X functional, while other functionals like PBE, TPSS and B3LYP are still not accurate enough for quantitative descriptions. (C) 2012 Elsevier B. V. All rights reserved.