A man was found in a critical condition at Pugneys Country Park.
Emergency services were called at 1.19pm on Monday and the man was airlifted to hospital.
Police said there are no suspicious circumstances surrounding the incident.
Detective Inspector Michelle Martin, of Wakefield District CID, said: “Police were called to a report of concern for safety in Asdale Road, Wakefield, at 1.19pm yesterday.
“A 34-year-old man was airlifted to hospital, where he remains today in a critical condition.”