We used scanning tunneling microscopy to examine the effect of introducing SCN- to the Pb monolayer island structure formed during the underpotential deposition (upd) of Pb on Au(111). In the absence of SCN-, upd of Pb initially leads to the formation of Pb islands exhibiting the same hexagonal structure and atom-atom spacing (0.34 nm) as does the Pb bulk deposit. Upon addition of SCN-, a new type of structure is formed, featuring linear rows of Pb adatoms, held apart from each other by SCN-, which are lying flat on the electrode surface. These linear Pb structures reflect templating by the ambidentate SCN- molecule.