In this paper, we determine the critical particle size and conductivity range that leads to pronounced eddy current effects on magnetization reversal of magnetic nanostructures. An extended finite-element micromagnetic solver which includes eddy currents is used to calculate the magnetization behavior of a permalloy nanocube of 27 nm side under the influence of an applied field. It is shown that for high-conductivity /spl sigma/>10/sup 6/ (/spl Omega/ m)/sup -1/ in the intermediate state of reversal it takes the magnetization longer to fully align in the direction of the applied field.