Using a parameterized density-functional method we have studied the structural and electronic properties of different II-VI and III-V semiconductor clusters. We studied finite parts of the zincblende and wurtzite crystal structure for CdS, CdSe, InP, and ZnO and allowed the structures to relax to the closest total-energy minimum. Both stoichiometric and non-stoichiometric naked clusters were considered. We found (i) that the relative stability of the zincblende- and the wurtzite-derived clusters depends on the size of the structure, (ii) that the total-energy per atom is a non-smooth function of the size, and (iii) a correlation between the size of the HOMO-LUMO bandgap and the stability of the cluster. The implications of these results for the experimental analysis of the size distributions are discussed. (C) 2002 Published by Elsevier Science B.V.