Adsorption of leucine and asparagine on Cu(1 1 1) surface has been studied by means of scanning tunneling microscopy (STM) in ultra-high vacuum (UHV) conditions. It has been found that leucine can form Q x 2) superstructure on Cu(1 1 1) and copper steps facet to < 1 1 0 > directions. On the basis of our STM images, model has been proposed for the Cu(1 1 1)(3 x 2)-leucine superstructure. The model explains quite naturally the motivation behind the step faceting process. On the other hand, asparagine cannot form any ordered superstructure on Cu(1 1 1) and no copper step faceting can be observed either. The role of amino group in the side chain played in asparagine adsorption geometry is discussed in this paper. (c) 2006 Elsevier B.V. All rights reserved.