Various embodiments of systems, methods, computer devices, and computer software are disclosed for implementing cross-platform targeted advertisements. One embodiment is a method for providing a targeted advertisement. One such method comprises: accessing one of a web site and a mobile site in an initial session; collecting information related to a user in the initial session; storing the collected information; accessing the other of the web site and the mobile site in a subsequent session; determining the user for the subsequent session based on the stored information; selecting a targeted advertisement for the subsequent session based on the stored information; and providing the targeted advertisement to the user in the subsequent session.