Objectives To investigate public perceptions of overdiagnosis and overtreatment in low-risk thyroid cancer and explore opinions regarding the proposed strategy to change the terminology of low-risk cancers. Design Qualitative study using focus groups that included a guided group discussion and presentation explaining thyroid cancer, overdiagnosis and overtreatment, and proposed communication strategies. Transcripts were analysed thematically. Setting Sydney, Australia. Participants Forty-seven men and women of various ages from a range of socioeconomic backgrounds with no personal history of thyroid cancer. Results Participants had low pre-existing general awareness of concepts of overdiagnosis and overtreatment and expressed concern regarding this new information in relation to thyroid cancer. Overall, participants understood why the strategy to change the terminology was being proposed and could see potential benefits including reducing the negative psychological impact and stigma associated with the term 'cancer'; however, many still had reservations about the strategy. The majority of the concerns were around their worry about the risk of further disease progression and that changing the terminology may create confusion and cause patients not to take the diagnosis and its associated managements seriously. Despite varied views towards the proposed strategy, there was a strong overarching desire for greater patient and public education around overdiagnosis and overtreatment in both thyroid cancer and cancer generally in order to complement any revised terminology and/or other mitigation strategies. Conclusions We found a strong and apparently widely held desire for more information surrounding the topic of overdiagnosis and overtreatment. Careful consideration of how to inform both the public and current patients about the implications of a change in terminology, including changes to patients' follow-up or treatments, would be needed if such a change were to go ahead.