The search has been extended beyond Scarborough and the North Yorkshire Police have now requested region-wide coverage.
Kimberley Grace Reavley, 25, of Londesborough Road, Scarborough, has not been seen since 6pm on Monday 2 July 2012, when she was seen by a friend on Victoria Road in the town.
Officers consider Kimberley to be vulnerable due to health issues and she is not believed to be in possession of her essential medication.
Kimberley is described as white with a stocky build and shoulder-length brown hair.
When she was last seen Kimberley was wearing a blue denim jacket, a cream jumper, light blue trousers and white sandals. She was carrying a blue rucksack.
Police believe that Kimberley is still in the Scarborough area.
Inspector Martin Dennison, of Scarborough Safer Neighbourhood Team, said:
I urge anyone who has seen Kimberley to contact the police as soon as possible so that we can confirm she is safe and well.”
If you can help to locate Kimberley Reavley please contact North Yorkshire Police on 101, select option 1 and pass the information to the Force Control Room.