Background: Creativity is an important skill for the future society and developing students' creativity is an important part of science education. Working on a creative science project may help developing students' creative abilities, and the interaction between teacher and students during the work on defining a problem and solving the problem, is an ideal forum for supporting students' creativity. Purpose: The purpose of the study is to get insight into how teachers respond to students' creative ideas during the works on a creative science project, and how the interaction between teacher and students may support or inhibit students' creative abilities. Design and methods: Data in this study consist of 49 videorecorded interactions between two teachers and student groups working on a science project with the aim of supporting students' creative abilities. The interactions were analyzed with the use of Conversation Analysis (CA). Results: Analysis shows that teachers play an important role in developing students' creative ideas. The analysis shows how teachers, after being told the students' creative ideas, evaluates the students' ideas as either preferred or dis-preferred according to the teacher's own preference. The teachers' evaluative stance towards the students' creative ideas determines how the conversations with the students unfold and make explicit which ideas the students should work further within the project. Conclusion: Controlling the conversation based on the teacher's own preference may lead to missed opportunities regarding converting students' mini-c creative ideas into little-c creative ideas. Being able to create time and opportunity to explore and develop students' ideas, there is a need for fewer students per teacher and more focus on the process aspect of creativity rather than the product aspect.