Abstract Background Surveys indicate quite high prevalence of cancer worry in the general population, but little is known about what it is about cancer that worries people. A better understanding of the origins of cancer worry may help elucidate previously found inconsistencies in its behavioural effect on cancer prevention, screening uptake, and help-seeking for symptoms. In this study, we explore the prevalence and population distribution of general cancer worry and worries about specific aspects of cancer previously identified. Methods A population-based survey of 2048 English adults (18–70 years, April–May 2016), using face-to-face interviews to assess demographic characteristics, general cancer worry and twelve sources of cancer worry (adapted from an existing scale), including the emotional, physical, and social consequences of a diagnosis. Results In general, a third of respondents (37%) never worried about cancer, 57% worried occasionally/sometimes, and 6% often/very often. In terms of specific worries, two thirds would be ‘quite a bit’ or ‘extremely’ worried about the threat to life and emotional upset a diagnosis would cause. Half would worry about surgery, radiotherapy, chemotherapy, and loss of control over life. Worries about the social consequences were less commonly anticipated: just under half would worry about financial problems or their social roles, and a quarter would be worried about effects on identity, important relationships, gender role, and sexuality. Women and younger people reported more frequent worry about getting cancer, and would be more worried about the emotional, physical, and social consequences of a cancer diagnosis (p