The posters, which will appear on 50 countries internationally, were created by South African agency Bester Burke after the shop won a competition that drew 300 entries. The creative is a young child's colourful drawing, showing her standing by her parents' graves.
Simultaneous events in London, New York and Johnnesburg will launch the billboard with Unicef, Clear Channel representatives and celebrities including Lord Richard Attenborough and Lord David Puttnam to attend.
Former James Bond star Roger Moore and comedy actress Whoopi Goldberg will attend the New York launch.
The Unicef aim is to raise awareness of the impact HIV and Aids has on children, highlighting the disease's impact in Africa.
According to the latest statistics, fewer than 5% of HIV positive children have access to the treatment they need and only 10% of pregnant women have access to services that prevent mother-to-child transmission of the virus.
Ann Veneman, executive director Unicef, said: "The Clear Channel Outdoor partnership will help make the public aware that children are the missing face of Aids."
The creative will run globally across 50 countries starting in November.
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