The extraction behavior of platinum(II), platinum(IV) and palladium(II) with an ionic liquid, 1-octyl-3-methylimidazolium hexafluorophosphate ([Omim][PF6]), and a quaternary ammonium salt, distearyldimethylammonium chloride (DSDMAC), as extractants has been investigated in a liquid-liquid extraction system. In the present experimental conditions, platinum was extracted selectively over palladium by both extractants. It was found that DSDMAC possessed a higher extraction ability for the metals than that of [Omim][PF6]; on the other hand, more effective separation of platinum and palladium was achieved using [Omim][PF6] than using DSDMAC. The composition of the complex between their metals and extractants was elucidated by slope analysis and Job's method. The metals exist as chloro anion complexes in a hydrochloric acid solution, which reacted with extractant molecules in chloroform and were extracted into the organic solutions. Furthermore, platinum could be separated from palladium in an acidic chloride medium using the ionic liquid as an extractant.