Children and teachers may not think in the same way about particular science concepts. Such parallel lines of thought can compound children's confusion and misunderstanding as they learn science at primary school. The situation could be more acute when student teachers are teaching science, because of their limited experience of considering children's ideas. This paper investigates children's and student teachers' ideas about certain science concepts: "animal", "flower", "living", "force" and "energy". The ideas and understandings of 96 children and 168 student teachers were explored. Results showed that the student teachers and children had similar ideas about "flower" and "animal", whereas they evidenced very different responses to "living", "energy" and "force". Implications for classroom practice are considered. (Contains 2 figures.)