We investigate the structural, electronic and magnetic properties of transition metal (TM = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, and Cu) doped (ZnO)(12) clusters (TMZn11O12 and TM2Zn10O12) by using density functional theory approach. All the substitutional doping clusters are of high stability and remain quasi-cage structures with the exception of Ti2Zn10O12 and V2Zn10O12. The doped TMZn11O12 clusters are magnetic except TM = Ti, whereas the TM2Zn10O12 clusters are either antiferromagnetic or paramagnetic, suggesting that concentration of TM dopant has great influence on the magnetism of the ZnO-based nanostructures. The magnetic behavior is understood from charge-transfer model and partial density of states. (C) 2009 Elsevier B.V. All rights reserved.