The electrodeposition of metal onto a low energy electrode surface like graphite or H-terminated silicon produces mesoscopic metal particles that are broadly distributed in diameter. Broad size distributions are observed even in cases where the nucleation of metal is temporally controlled. For this reason, electrodeposition has been infrequently used as a means for obtaining metal nanostuctures. The central problem is the diffusional "cross-talk" that exists between neighboring metal nanostructures on the electrode surface. Evidence for this diffusional interparticle coupling is encoded into,particle size and position distributions obtained from experimental data and from Brownian Dynamics computer simulations of nanostructure growth. Diffusional cross-talk between nanostructures can be turned off using either of two growth strategies described in this paper. These methods permit the size-selective electrodeposition of metal nanoparticles and nanowires that are narrowly distributed in diameter.