The parents of four-year-old Madeleine McCann are backing a scheme to trace missing children using the social networking websites Facebook and Bebo.
Kate and Gerry McCann have welcomed the initiative by charity Missing People, which will mean Facebook users can view details of missing youngsters on their own page.
In a statement the couple said: "We strongly support and encourage this new initiative to use Facebook to increase awareness of missing children.
"Using the power of social media in this way will undoubtedly capture the attention — and hopefully the help — of a younger population who are a hugely valuable and resourceful group.
"We would urge the millions of Facebook users around the world to keep looking and to do what they can to help bring these children home.
"This initiative by Missing People, British Telecom and all those supporting them, is another highly commendable and positive step in protecting and helping children."
Missing People has set up an application for Facebook users to download, which will mean information on current appeals will be displayed on their homepage.
The charity is also joining Bebo's "Be Cause", an internet site which gives information for young people about charities and campaign groups, to publicise its 24-hour Runaway Helpline.
It hopes to access millions of internet users in its quest to find thousands of youngsters who go missing each year.
The charity's own website has attracted 40 million "hits" in the year since it was launched, and Missing People already posts film clips on YouTube.
Missing People Chief Executive Paul Tuohy said: "If every Facebook user downloaded our BT-powered application, millions of people internationally could see an appeal that could help us to reunite a family."
In the last 12 months Missing People has dealt with 13,000 queries about under-18s who have vanished, including 2,000 about children under 13.
It is launching the new scheme to coincide with International Missing Children's Day today, which will see a number of cases highlighted including the disappearance of Madeleine McCann.
Other missing youngsters being brought back into the spotlight are Paige Chivers, a 15-year-old who went missing from Blackpool last year, and Andrew Gosden, 14, who was last seen at King's Cross train station in September.
International Missing Children's day was created to mark the abduction of six-year-old Etan Patz in New York in 1979, who has never been found.