グループN
Rantanen began rallying in 2003 in his native Finland. In 2004 and 2005 he competed in the Finnish Junior Rally Championship, and the main Finnish Rally Championship in 2005 and 2006. In 2005 he competed in his first World Rally Championship round on Rally Finland, winning the Group N category (for less powerful Group N cars). He repeated this feat in 2006, also winning the Group N class in the Finnish Rally Championship. He moved up to the Group N category in the Finnish championship in 2007, finishing sixth. He finished fourth in the following year, 2008. On the 2008 Rally Finland, Rantanen drove a Ford Focus WRC to seventh overall.