North Yorkshire Police has today issued an appeal to find Sophie Thornton, 16.
She was last seen in Scarborough town centre at around 11am yesterday.
The force said she is believed to have travelled to the Harrogate area with a 17-year-old boy.
Officers are" extremely concerned" for her safety and are appealing to anyone who has seen her or knows where she is to contact them.
She is described as 5ft 5ins tall, of slim build with brown hair and grey eyes.
Anyone who has seen Sophie or knows where she is, is asked to call North Yorkshire Police on 101.
If anyone actually sees her, they are asked to call 999.
Give the reference number 12180179508 when passing on information.