The effect of surface reconstruction on work function of a quasi-hexagonal reconstructed Pt(1 0 0) surface has been studied by local tunneling barrier height (LBH) imaging with scanning tunneling microscopy (STM). Relatively low LBH is observed at the areas providing the strongly-corrugated geometric structure, where the bright contrast is observed in the STM image. This reduction in the local work function has been interpreted in terms of the dipoles induced by the Smoluchowski smoothing effect. This suggests the reason why the macroscopic work function of the reconstructed Pt(1 0 0) surface is lower than that of the Pt(1 1 1) surface, despite the similar hexagonal surface structures. (C) 2004 Elsevier B.V. All rights reserved.