Mammographic screening is offered to many women under 50 in the UK who are at moderate or high risk of developing breast cancer because of their family history of the disease. Little is understood about the impact of screening on the emotional well-being of women with a family history of breast cancer. This qualitative study explores the value that women at increased risk placed on screening, both pre- and post-cancer diagnosis and the impact of the diagnosis. In-depth interviews were undertaken with 12 women, aged 35-50, diagnosed with breast cancer while on an annual mammographic screening programme. Women described the strong sense of reassurance gained from screening prior to diagnosis. This faith in screening was reinforced by early detection of their cancer. Reactions to diagnosis ranged from devastation to relief at having finally developed a long-expected condition. Despite their positive attitudes about screening, not all women wanted to continue with surveillance. For some, prophylactic mastectomy was preferable, to reduce future cancer risk and to alleviate anxieties about the detection of another cancer at each subsequent screen. This study illustrates the positive yet diverse attitudes towards mammographic screening in this group of women with a family history of breast cancer.