Abstract: Teaching for conceptual understanding is one aim of the problem solving curriculum. The fist part of the article describes a study that aimed to identify potential factors that may prevent pre-service primary school teachers from teaching the topic of volume for conceptual understanding. The study involved ninety-five non-graduate pre-service teachers. Their responses to a paper-and- pencil instrument were used to identify possible obstacles to teaching for conceptual understanding. The possession of a narrow range of experiences related to a concept, the possession of procedural knowledge based upon weak conceptual knowledge and the reluctance to from mental representation of a concept emerged as possible obstacles. The second part suggests ways to facilitate pre-service teachers teaching the topic of volume for conceptual understanding.