The ScmOn- (m = 2-5, n = 2-3) cluster anions were investigated using photoelectron spectroscopy and density functional theory (DFT) calculations. The adiabatic detachment energies (ADEs) and vertical detachment energies (VDEs) of these cluster anions were estimated from their photoelectron spectra. The most probable structures of ScmOn (m = 2-5, n = 2-3) cluster anions and neutrals were determined by combining DFT calculations with the photoelectron spectroscopy experiments. The structures of ScmOn- (m = 2-5, n = 2-3) can be characterized as attaching oxygen atoms to the top sites, bridge sites, or hollow sites of Scm clusters. There is no direct interaction between the oxygen atoms. (C) 2013 Elsevier B.V. All rights reserved.