Katrice Lee - Missing for more than 30 years
17 June 2013 Last updated at 04:44 BST
It is thought at least eight million children go missing around the world every year, and while usually the child is found quickly the ordeal can sometimes last months, even years.
BBC News has been speaking to families in different parts of the world who have been affected by a missing child.
Babita Sharma went to Gosport in the south of England to meet Sharon Lee, whose daughter has been missing for more than 30 years, after disappearing in Germany on her second birthday.