We report a study of the nonmetal–metal transition of free-standingPdN clusters(2≤N≤21) carried out through two different theoretical approaches that are extensivelyemployed in electronic structure calculations: a semi-empirical tight-binding (TB)model and an ab initio DFT pseudopotential model. The calculated critical sizefor the metallic transition decreases rapidly with the temperature and anoscillatory dependence with the cluster size is obtained, particularly in the DFTapproach. The TB model describes the metallic behavior for cluster sizes beyondN≈12 well. Our obtained critical size at room temperature is of the order of the experimentalestimation.