The service, TV Cabo Interactiva, is based on set-top boxes running Microsoft software and offers digital video-recording facilities, email, home shopping and internet access.
It is the third commercial interactive TV service based on Microsoft's TV Advanced software, and the first to use broadband cable. It is available to 800,000 homes in the Lisbon area and, in September, will be available to 1m homes.
The same system was due to be delivered last autumn to Europe's largest cable operator, United Pan-Europe Communications, but missed deadlines meant that the rollout never happened.
www.microsoft.com
www.tvcabo.pt