Graham Roskell, aged 65, was reported missing on the morning of Saturday 3 November 2012, after leaving Harrogate District Hospital, where he was receiving treatment.
Officers have been conducting extensive searches for Mr Roskell, however he has still not been found.
West Yorkshire Police assisted yesterday evening with the air support Helicopter and Mountain Rescue have been search fields around Harrogate.
Residents of Harrogate and the surrounding areas are being urged to check sheds, outbuildings and garages in case Mr Roskell has taken shelter in them over night.
Inspector Bruce Prendergast, of Harrogate police, said:
Mr Roskell has been missing overnight and we need to find him urgently.
He may have taken shelter somewhere as the night drew in and I would urge everyone to take a few minutes to check their outbuildings and help us with our search.
Mr Roskell is white, with a stocky build and short grey hair.
When he was last seen he was wearing a green patterned jumper, green trousers, black shoes and a blue dressing gown.
An image of Mr Roskell may be released shortly following agreement from his relatives
Anyone who can help locate Mr Roskell is urged to contact North Yorkshire Police on 101 – select option 2 – and ask for Harrogate police.