Rubuta ci gaba don wannan sakin layi - A matsayin memba na manyan 'yan wasan kasar Girka, Diamantidis ya lashe lambar zinare ta EuroBasket a shekarar 2005; yayin da yake kafa tsaro wanda ya ba da izinin maki 59.7 kawai a kowane wasa. Ya kuma zira kwallaye uku wanda ya rufe makomar wasan kusa da na karshe da Faransa, 'yan sakanni kafin buzzer na karshe na wasan. Ya kuma jagoranci wannan gasar a cikin taimakawa, kuma ya kasance wani ɓangare na All-EuroBasket Team. A shekara ta 2006, ya taka muhimmiyar rawa a gasar cin kofin duniya ta FIBA, inda Girka ta mamaye Team USA a wasan kusa da na karshe, kuma Diamantidis ya kammala a matsayin jagoran gasar. Diamantidis kuma ya kasance dan wasan Olympics sau biyu, kamar yadda ya sa launuka na Girka a 2004 da 2008
, kuma a lokuta biyu sun sami matsayi na biyar na gasar, wanda ya yi daidai da mafi kyawun ƙarshen lokaci ga Girka. Dangane da nasarorin da ya samu, an nada shi dan wasan Mister Europa na shekara ta mujallar wasanni ta Italiya Superbasket a 2007. An kuma kira shi Dan wasan Girka na shekara a shekara ta 2007.