Spin-polarized density functional theory calculations on bimetallic Con-1Mn and Con-1V (n = 2-9) clusters are reported. The clusters exhibit high stability at n = 6. With the exception of CoV, the magnetic moments of Con, Con-1Mn and Con-1V increase with size by 3 mu B for n = 2-5 and by 1 mu B afterwards. The magnetic enhancement (reduction) is identified upon Mn (V) substitution, compared to Con, consistent with recent experimental observation in large-sized clusters. Their different magnetic behavior of Mn and V-substituted clusters results from both differences in magnetic alignment (ferromagnetic in Con-1Mn and ferrimagnetic in Con-1V) and reduced local moments on Co in Con-1V. (C) 2008 Elsevier B. V. All rights reserved.