The station lies in London Underground zone 1 and is on five different lines. On the Circle Line and Hammersmith and City Line it is between Great Portland Street and Edgware Road. On the Metropolitan Line it is between Great Portland Street and Finchley Road. On the Bakerloo Line it is between Regent's Park and Marylebone, and on the Jubilee Line it is between Bond Street and St John's Wood.
The sub-surface Circle Line platforms are part of the very oldest Underground line, and of the stations on this section of line they are perhaps the best-preserved. Plaques along the platform show old plans and photographs of the station.
The station layout is rather complex. The sub-surface station is connected to the open-air Metropolitan Line station. This is a terminus for most trains, but there is also a connecting curve that joins to the Circle Line just beyond the platforms.
Below this is a deep-level tube station for the Bakerloo and Jubilee Lines. These are arranged in a cross-platform interchange.