Going beyond mere forum posts categorization is key to understand why some students struggle and eventually fail in MOOCs. We propose here an extension of a coding scheme and present the design of the associated automatic annotation tools to tag students’ questions in their forum posts. Working of four sessions of the same MOOC, we cluster students’ questions and show how the obtained clusters are consistent across all sessions and can be sometimes correlated with students’ success in the MOOC. Moreover, it helps us better understand the nature of questions asked by successful vs. unsuccessful students.