[kreetx]

I regret being that loose with the designation :), Romanian and Hungarian are valid counter arguments.

In my mind, I was thinking of the belt of countries between Russia and Central Europe, starting from the Baltics down to the Balkan (excluding Greece).

[NicuCalcea]

Even by your definition, I can count at least seven countries where the official language is not Slavic. And that's not even including all the Altaic, Romance and other assortment of regional languages, many of which have some sort of official status.