[Ichthypresbyter]

Depends which Eastern Europeans- Lithuania stayed pagan until the late 14th century, with some areas not being Christianised until the early 15th century.

Of course, the Lithuanians themselves might well say they're not Eastern European...

[aguaviva]

Why would they? They're Balts, and quite homogenously so. Their ancestors were likely centered a bit further East, but not that far out. And their language appears to have split off from a common ancestor of the the Slavic languages.

[paganel]

Wanted to add an aside about the Lithuanians and them not becoming Christian until the 1300s, but, as you said, some Lithuanians themselves might have said that they're not Eastern-Europeans :)