The adsorption of water and ammonia molecules to Na-n (n = 7, 18, and 25) clusters was studied using density functional theory calculations. Calculated adsorption energies are small (<0.4 eV) and vary according to bonding site on the cluster. A recently-developed site-specific analysis of cluster polarizability was used to investigate the correlation between adsorption energy at various binding sites and the corresponding site polarizabilities. The results show that adsorption energies for these molecules are largest at sites corresponding to surface atoms with the largest polarizabilities, indicating that site-specific polarizabilities can be used to predict the most favorable adsorption sites. (C) 2011 Elsevier B. V. All rights reserved.