What major/concentration is Blair studying at NYU?

First, she's not in NYU anymore, she's now at Columbia :)

Second we don't know, it's a mystery i hope we could find out later though.

i think she's taking pyshcology. watch episode 21 season 3..i think they mention it there. i' not so sure..=)

i think it's history of art because she had a test once on that