We report the electrochemical preparation of cadmium selenide nanoparticles at gold electrodes modified with molecular templates. The molecular templates were obtained by properly arranging thiolated beta -cyclodextrin self-assembled monolayers (SAMs) on gold electrodes. Selenium was first deposited on a SAM-modified gold electrode at an appropriate potential, followed by reduction to HSe- in a solution containing Cd2+, leading to the deposition of CdSe. The Cd codeposited at the time of CdSe deposition was removed by anodic dissolution at a potential where it was oxidized. Scanning electron microscopic pictures showed that Se-0 and cadmium selenide particles of smaller than 60 and 150 Mm diam, respectively, were deposited on the SAM-modified gold electrodes. Selenium particles of as small as 1-2 nm diam and similar to0.2 nm height were observed by in situ electrochemical scanning tunneling microscopy experiments during the early stages of electrochemical deposition.