In this chapter, we consider how problem posing forms an integral part of mathematical modelling and consider its placement during modelling processes. The problem and its formulation is an essential part of modelling, and a modelling process is usually associated with a continual adjustment and reformulation of the main problem. In addition, one may formulate conjectures, ask monitoring and control questions, and have a critical stance toward the model and its results. We consider how the educational intention of the modelling activity and the placement in the modelling cycle relates to the problems and questions being posed. We briefl y consider how problem posing may be implemented in mathematical modelling through the use of students' conjectures and by students acting as consultants and clients.