Dr O'Farrell specialises in gastroenterology and is accredited in endoscopy and colonoscopy. He has an interest in liver disease and prevention of bowel cancer. He consults at North Shore Private Hospital and at his rooms in Mona Vale. and does procedures at Mona Vale Public Hospital, North Shore Private, Warringah Mall Day Surgery and Dee Why Endoscopy. Dr O’Farrell delivers treatment for viral hepatitis through his work at Liver Clinic at Royal North Shore Hospital