The first stages of platinum electroless deposition on p-Si (100) from hydrogen fluoride (HF) solutions are studied by atomic force microscopy (AFM), transmission electron microscopy (TEM), electron dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). Platinum nuclei are deposited on a silicon substrate by simple immersion in an aqueous HF solution containing a platinum salt. Tapping-mode AFM and TEM have been used to characterize the samples morphologically, and EDS and XPS to identify the chemical nature of the main features. Platinum silicide formation has been detected for the first time in this kind of process, suggesting a competition between the deposition of pure metal and the formation of its silicide.