Best Selling might be hard to research and would more than likely need eBay's help but the most listed items can be easily found out......CD's, Tapes and Records are by far and a way the most listed items with at the time of this reply having 142,475 items in that sub-section.....the only things that come anywhere near are Clothing & Accessories - 153,574, Books, Comic & Magazines - 112,292 and DVD, Film and TV - 117,206 but these are all complete sections with further divisions in their respective groups my guess would be CD's would be the best selling things...reasonable prices to buy and low postage may account for that popularity.