Examples to determine media impressions using distributed demographic information are disclosed. An example apparatus includes a communication interface to receive a network communication at an impression monitor system based on a login event at a client device, the login event associated with an Internet-based service of a first Internet domain different from a second Internet domain of the impression monitor system. The example communication interface also sends a response to the client device, the response to cause the client device to include first and second cookie identifiers in a login reporting message and to send the login reporting message to a computer of a database proprietor that provides the Internet-based service, the first cookie identifier associated with the first Internet domain of the Internet-based service, and the second cookie identifier associated with the second Internet domain of the impression monitor system.