Using gradient-corrected density functional theory, we have comparatively studied the adsorption properties of diatomic molecules N2 and NO on vanadium clusters up to 13 atoms. Spontaneous dissociation is found for N2 adsorbing on Vn with n = 4–6, 12, and for NO with n = 3–12, respectively, whereas for the rest of the clusters, N2 (NO) molecularly adsorbs on the cluster for all the possible sites. The incoming N2 retains the magnetism of Vn except for V2 and V6 whose moments are quenched from 2 μB to zero. Consequently, the moments of VnN2 (n = 2–13) show even/odd oscillation between 0 and 1 μB. On the adsorption of NO, the magnetic moments of Vn with closed electronic shell are raised to 1 μB at n = 4, 8, and 10, and 3 μB at n = 12, whereas for open shell clusters, their magnetic moments increase for n = 5 and 9 and decrease for n = 2, 3, 5–7, 11, and 13 by 1 μB. These findings are rationalized by combinatory analysis from several aspects, for example, the geometry and stability of bare clusters, charge transfer induced by the adsorption, feature of frontier orbitals, and spin density distribution. © 2012 Wiley Periodicals, Inc.