Lehtonen, who started for the Uuraisten Urheilijat, won second place with the relay at the Svenska Skidspelen in Falun in 1961 . In the following year she won the bronze medal at the Nordic World Ski Championships in Zakopane in 1962 and finished in fifth place over 5 km and over 10 km. In March 1962 she won the Lahti Ski Games over 10 km. In the same year she was second in the Svenska Skidspelen over 10 km and first with the relay. In 1963 she came second at the Lahti Ski Games over 10 km and at the Svenska Skidspelen on second place with the relay and also on first place over 10 km. At her only participation in the Olympicsin February 1964 in Innsbruck she won the silver medal over 5 km and bronze with the 3x5 km relay. Over 10 km she achieved tenth place there. At the Svenska Skidspelen 1964 in Kiruna she was second with the relay. In her last year as an active cross-country skier in 1965, she won the Svenska Skidspelen with the relay and over 10 km. In March 1965 she achieved third place over 10 km at the Lahti Ski Games. In Finnish championships she won three times over 10 km (1961-1963) and twice over 5 km (1963, 1964).