Sussex Police is concerned for a teenager missing from Worthing Hospital since Friday (November 8).
According to police, 15-year-old Mia Thornton, from Lancing, has not been seen since leaving Worthing Hospital last week.
She is described by police as white, 5ft 3ins tall, slim and with blonde shoulder-length hair often worn in a bun.
She was last seen wearing a pink coat with pink fur around the hood, police said, with black tracksuit bottoms and grey, white and black striped Nike trainers.
Mia lives in Lancing but has links to Shoreham, Wick and Arundel, police added.
PC Paul Gwyn said: "We are concerned for the welfare of Mia due to her age and vulnerability. Please let us know if you have seen her or have any information about her whereabouts."
Report online or ring 101 quoting serial 1655 of 06/11.