As a member of the junior national basketball teams of Greece, Papantoniou won the gold medal at the 2008 FIBA Europe Under-18 Championship and the silver medal at the 2009 FIBA Under-19 World Championship.
Papantoniou won the gold medal at the 2008 FIBA Europe Under-18 Championship at the 2009 FIBA Under-19 World Championship. This was as a member of the junior national basketball teams of Greece. Papantoniou won the gold medal at the 2008 FIBA Europe Under-the silver medal at the 2009 FIBA Under-19 World Championship. This was as a member of the junior national basketball teams of Greece.