Philip Cairns (born 1 September 1973) disappeared on the afternoon of 23 October 1986 while walking back to school in south Dublin, Ireland.
The 13-year-old schoolboy left his home in Ballyroan to return to school, but has not been seen since.
A large-scale investigation was carried out but no trace of the boy has ever been found.
His disappearance is now treated as a high-profile child murder case, the only similar incident in Ireland being the murder of Robert Holohan in January 2005.
It is one of the most high-profile disappearances in recent Irish history.Philip's family have issued numerous appeals for information.
A reconstruction took place in 2007 and was later televised on RTÉ One, while a reward of €10,000 has also been offered.
The book, When Heaven Waits, published in 2007, featured an interview with Philip's mother.