 In 2003 Vos successfully defended her national junior mountain bike title.At the time trial championships she again finished second, this time behind Maxime Groenewegen while 2002 champion Roxane Knetemann finished fourth.Vos excelled in cyclo-cross for the first time in 2004 when she won her first international race in Gieten, beating Birgit Hollmann and Arenda Grimberg.