Blended learning can facilitate many opportunities about usage of online discussion for different purposes. As a tool in blended learning, online discussions widen the walls of classroom discussions in a virtual manner. Especially, in teacher education programs case based discussions are very helpful for pre-service teachers to practice real-life situations. By this way, the link between theory and practice can be established. This study aims to examine the pre-service teachers' experiences about three different discussion structures in a case based blended learning environment. This study also explored their thoughts toward the effects of online discussion on their professional development and their suggestions to increase the effectiveness of online discussion. The participants of this study were 14 pre-service teachers from the department of Early Childhood Education (ECE) of a funded university. The six open-ended questions were asked in order to explore the opinions of the pre-service teachers. The qualitative data were analyzed through the matrix displays. (Contains 1 figure.)