Kostner had his first international success in January 1998 at the Nordic Junior World Ski Championships in Pontresina . There he won the bronze medal with the relay. He was also fifth in the 30 km classic and 10 km freestyle. In the following year he took 23rd place over 10 km classic and fifth place over 30 km freestyle at the Nordic Junior World Ski Championships in Saalfelden . In March 1999 he ran in Candanchú for the first time in the Continental Cup and achieved 17th place over 15 km classic. By 2004 he had four second places and 11 wins in the Continental Cup and won the overall standings in the 2003/04 season. He had his debut in the cross-country skiing world cup in March 2000 in Lahti , which he finished in 56th place in the sprint. At the beginning of the 2000/01 season he got his first World Cup points in Santa Caterina Valfurva with 12th place over 15 km freestyle. In the further course of the season he came in the points five times and reached 64th place in the overall World Cup. This was his best overall placement in the World Cup. In March 2004 he achieved his best placement in the World Cup with sixth place in the 30 km freestyle in Pragelato . In the 2005/06 season he achieved third place in the overall ranking of the Alpine Cup with eight top ten results, including two victories . In the following season he was third three times and took 19th place in the overall Alpine Cup ranking. In the 2007/08 season he was in the top ten 14 times in the Alpencup. He achieved third place three times and second three times. He also triumphed in the 20 km freestyle in Capracotta and in the 15 km mass start race in Pokljuka and won the overall standings. After third place in the 15 km mass start race at the Alpine Cup in Alta Badia at the beginning of the 2008/09 season, he finished third twice, second once, and twice and first place and thus won the overall ranking of the Alpine Cup again. At the 2009 World Cup final in Falun , he came in 30th. He completed his last World Cup race in December 2009 in Davos , which he finished in 77th place over 15 km freestyle. From the 2011/12 season until his last active season 2014/15, he mainly started in the Marathon Cup . He finished third at the Transjurassienne in February 2012 and reached sixth place in the overall standings at the end of the 2011/12 season. In 2006 he also won the Gsieser-Tal-Lauf , in 2007 the Marcialonga Light over 40 km classic and in 2013 the Demino Ski Marathon and the Toblach-Cortina .
Italy
Goms
Altenmarkt
Candanchu
Pokljuka