The adsorption structure of N2O on Pd(110) was analyzed below 14 K by scanning-tunneling microscopy. The N2O monomer was oriented along the [001] direction in the on-top form. Furthermore, the formation of small aggregates extending along the [110] direction was observed. The observed images were well-simulated for two types of cluster structures optimized by density-functional theory calculations. The components in the aggregates are proposed to be in a tilted form either on bridge sites or on-top sites. (c) 2005 Elsevier B.V. All rights reserved.