Tube users are able to watch moving advertising images and film trailers while they wait for their next train.
The high quality images, the size of a 14ft (168in) TV screen, are being projected on walls opposite platforms at five London Underground stations.
Piccadilly Circus, Euston, Bank, Liverpool Street and Bond Street have been fitted with the High Definition projectors and giant soundless screens.
It follows a successful trial at Euston tube station.
Richard Parry, from London Underground, said: "We believe that this technology will enhance passengers' journeys.
"The Tube has a history of innovation; these hi-tech screens are a perfect complement to the major upgrade work carried out by London Underground in delivering a world-class Tube for a world-class city."
Further stations are due to host the new cross-track projection (XTP) technology which allows the digital images to be projected on the walls opposite platforms.
This will take the number of screens to 150.
Any profits London Underground receive from XTP will be reinvested by London Underground to improve the Tube.
London Underground and CBS, which has installed the system, have been developing XTP for more than three years.