Platinum films electrodeposited from 10 mM H2PtCl6 have been probed using scanning electron microscopy (SEM) and ex situ scanning tunneling microscopy (STM) to examine morphological changes produced when Pb(II) is added to the deposition solution. Deposition was carried out potentiostatically at -250 and -1000 mV (vs Ag/AgCl) from solutions containing three different Pb(II) concentrations: 0, 0.05, and 0.4 mM. The presence of Pb(II) produced an extremely rough, spiky morphology on the nanometer scale and suppressed dendritic aggregation on the micrometer scale. These observations are interpreted in terms of Pb(II) counteracting enhanced surface diffusion of Pt atoms resulting from interaction between them and chloride ions at the solution/electrode interface.