At age thirty-five, Smyth made her official debut for the 2008 Summer Olympics in Beijing, where she competed in the women's marathon, along with her teammates Benita Johnson and Lisa Weightman. She successfully finished the race in forty-fourth place by fifteen seconds ahead of Spain's Yesenia Centeno, with a time of 2:36:10. She also ran in the marathon at the 2006 Commonwealth Games, coming in seventh place.