Examples to determine media impressions using distributed demographic information are disclosed. Some disclosed example methods involve sending a request to an impression monitor system in response to detecting a login event at a client device. The login event is associated with an Internet-based service of a first Internet domain different from a second internet domain of the impression monitor system. Such disclosed example methods also involve sending a login reporting message to a database proprietor that provides the Internet-based service. The login reporting message including first and second cookie identifiers. The first cookie identifier is associated with the first Internet domain of the Internet-based service, and the second cookie identifier is associated with the second Internet domain of the impression monitor system.