Carbonaceous deposits of diesel engine piston are known to reduce engine durability and performance. Little research has been conducted on the deposits removal by laser technique. In this paper, the deposits on the surface of piston crown part before and after laser cleaning were examined by FTIR, XPS and SEM/EDX. The deposits were found to be distributed non-uniformly on the surface and they could be distinguished as a thicker layer of contaminants, located mainly in the plug region, while a thinner layer can be found in the remaining area. The main constituents of the deposits were analyzed as Fe3C, Fe3O4, possibly FeOOH, oxygenated hydrocarbons as well as carboxylates. Laser cleaning can remove Fe3C completely, and reduce the concentration of oxygenated hydrocarbons and carboxylates significantly. Fe2O3, instead of Fe3O4, was formed on the cleaned region. (C) 2013 Elsevier B. V. All rights reserved.