Prouct page images different size to listing page?

Hi. I'd Like to make the image size for my product pages different to the image size on a listings page. At the moment i can't see a way to do this.

You'll notice on the first attached screenshot (eg1, which shows a listings page) that the image for Black Dress is the same size as the same image on the second screenshot (a product page). How do i set it so the listings page displays a different size image to the product page (but not the same size as the thumbnail image seen at the right of eg2)?

Thanks.

Help needed asap please.

I know this already. The problem I'm having is that the Image Size options sets the size for the image in listings pages and on product pages. I want the size to be different on these two page types. For example, on this website> www.asos.com/Women/Dresses/Cat/pgecategory.aspx?cid=8799 you can see that the images on this listing page are all a set size. If you click on one you'll be taken to it's product page where the image is bigger than it was on the listings page. This is what i want to achieve but, as far as i can tell, setting the image size on hikashop (under the "files" tab) sets one size for both the listings and product page. How can i set a different size for images when they are on a listings page to when they are on a product page?

Thanks very much. My confusion was with the term thumbnail. I thought that only referred to the size of the image when it showed up in the lightbox when clicked on the product page. Much appreciated