Adsorption of carbon monoxide on different Ag+-exchange sites of Ag-ZSM-5 zeolite has been investigated using density functional theory. The coordination and local geometry of the Ag+ ion in Ag-ZSM-5 as well as adsorption structures and energies of CO adsorbed on these sites are explored extensively. The structure of Ag+-exchange sites, location of the Al atom on the T site, and number of the Al atoms contained in the sites are considered in the theoretical calculations. The calculated results show that the Ag-O coordination number of two is strongly preferred before and after CO adsorption. The Ag-O bond lengths are in a broad range of 2.2-2.9 angstrom, and the Ag-C bond lengths for CO adsorbed on Ag-ZSM-5 zeolite are calculated to be 2.0-2.2 angstrom. Both Ag-O and Ag-C bond lengths for CO-Ag-ZSM-5 complex are longer than those for CO-Cu-ZSM-5 complex. The calculated adsorption energy of CO adsorbed on the I2 sites is between 28.5 and 29.6 kcal/mol, and that on the Z5, Z6, M5 and M6 sites containing one Al atom on the T position is between 11.3 and 18.9 kcal/mol whereas the calculated adsorption energy of CO adsorbed on the M7 site containing one Al atom is 19.9 kcal/mol. The introduction of the two Al atoms to the Ag+-exchange site results in a reduction of CO adsorption energy. In general, the adsorption energy of CO on Ag-ZSM-5 is lower than that on Cu-ZSM-5. The predicted coordination of the Ag+ ion, bond lengths of Ag-O and Ag-C as well as adsorption energy are in accord with available experimental results. (C) 2012 Elsevier B. V. All rights reserved.