According TTMIK Level 4 Lesson 10 :When you are saying "among" in the sense "popular among friends" or" famous among teenagers" you use the expression 사이에서 When you are referring to the actual physical space between two objects or two people, you can say 사이에

친구들 사이에서 인기가 많아요.

Francisco's answer is perfect as I'm Korean.

Thank you Mojave ^^ i'm still waiting for a native's explanation :(

I think either is correct. We should get a native's reply. For instance, 학생들 사이에 인기가 있는 선생 is an example from daum.net