Background The purpose of this study was to identify how the topic of overdiagnosis in breast cancer screening is framed by experts and to clarify differences and similarities within these frames in terms of problems, causes, values and solutions. Methods We used a qualitative methodology using interviews with breast screening experts across Australia and applying framing theory to map and analyse their views about overdiagnosis. We interviewed 33 breast screening experts who influence the public and/or policy makers via one or more of: public or academic commentary; senior service management; government advisory bodies; professional committees; non-government/consumer organisations. Experts were currently or previously working in breast screening in a variety of roles including clinical practice, research, service provision and policy, consumer representation and advocacy. Results Each expert used one or more of six frames to conceptualise overdiagnosis in breast screening. Frames are described as: Overdiagnosis is harming women; Stop squabbling in public; Don't hide the problem from women; We need to know the overdiagnosis rate; Balancing harms and benefits is a personal matter; and The problem is overtreatment. Each frame contains a different but internally coherent account of what the problem is, the causes and solutions, and a moral evaluation. Some of the frames are at least partly commensurable with each other; others are strongly incommensurable. Conclusions Experts have very different ways of framing overdiagnosis in breast screening. This variation may contribute to the ongoing controversy in this topic. The concept of experts using different frames when thinking and talking about overdiagnosis might be a useful tool for those who are trying to negotiate the complexity of expert disagreement in order to participate in decisions about screening.