 Kọ itẹsiwaju fun paragirafi yii - Pääjärvi ṣe agbekalẹ orilẹ-ede rẹ fun Sweden ni ọdun 14 pẹlu ẹgbẹ labẹ-16 lakoko akoko 2005-06; ni akoko ti o tẹle, o di oludari igbelewọn fun U16s. Ní àsìkò 2008 World Junior Ice Hockey Championships : Ni Pardubice ati Liberec, Czech Republic, ni ọdun 16 ati oṣu mẹjọ, o di oṣere ti o kere julọ ti o ṣere fun Sweden lakoko idije Hockey Junior World Championship. Nigba idije naa, o gba goolu kan, o si ṣe iranlọwọ fun Sweden si ipari nigbati o ṣe iranlọwọ fun Mikael Backlund lori goolu ti o ṣẹgun ere ti Sweden lodi si Russia ni ipari ipari. 