This study proposes a framework for investigating how preservice mathematics teachers notice students' reasoning about comparing distributions, including preservice teachers' attention to statistical elements used by students, interpretation of students' understanding, and decision about how to respond to students' statistical reasoning. The framework is illustrated with examples from interviews with six preservice teachers and used to analyse the preservice teachers' noticing of students' reasoning. Using the framework, the current study demonstrated that preservice teachers' attention to non-statistical elements and their struggles with interpreting the students' understanding seemed to prevent them from deciding how to respond to the students' existing understanding of variability. The ways in which this framework can be used to examine preservice and inservice teachers' noticing of students' statistical reasoning and to describe the development of their noticing expertise are discussed.