Police and the family of missing 17-year-old Aoife O'Hare, who is from the Cookstown area, are becoming increasingly concerned for her welfare.
Aoife was last seen in the Market Square area of Dungannon around 8.40am on Monday morning.
It is believed that she may have travelled to the Republic of Ireland and could be in Dublin.
She is described as 5ft 2, with long light brown/blond hair and when last seen she was wearing a blue jumper with pink writing, black trousers and carrying a cream coloured satchel with laptop.
Police are appealing to Aoife or anyone who knows of her whereabouts to contact Police in Dungannon on 101 quoting reference 1012 of 24/04/17.