Coquitlam RCMP say Kurt Derkson, 58, was on a day-pass to his brother's home in Richmond, but disappeared while his brother was pre-occupied sometime around noon on Thursday.
Derksen is described as white, five feet nine inches tall, and 201 pounds. He has short brown hair, a full beard, blue eyes and was possibly wearing glasses. Police suspect he may be heading to the airport.
Neighbours have raised concerns about security at the hospital. In the last three years, 43 patients have failed to return on time while on day leave, and four attempted to escape. One patient is still at large after failing to return from a day pass in May.
The 190-bed facility, which has a maximum security wing, houses some of the most dangerous offenders in the province, sent there because the courts have found them not criminally responsible for their offences due to mental disorders.