PurposeNine hundred female adolescents and young adults (AYAs) aged 15–39 are diagnosed with cancer in Denmark annually. Advances in cancer therapy have led to increased long-term survival; however, a serious side effect of cancer therapy is reduced fertility. The aim of our study was to explore the thoughts about fertility among female AYAs with cancer.MethodsOur study was conducted from September 2020 to March 2021 at the Copenhagen University Hospital, Rigshospitalet. Inclusion criteria were female AYAs with cancer aged 18–39. Twelve individual, semi-structured, qualitative interviews were performed with female AYAs with cancer (20–35 years). Data were analysed using thematic analysis.ResultsFour main themes were found: (1) the female AYAs held on to a hope of having children in the future; (2) the female AYAs experienced time pressure and waiting time as a sprint as well as a marathon; (3) the female AYAs faced existential and ethical choices about survival and family formation; and (4) the female AYAs felt a loss of control of their bodies.ConclusionOur study contributes with knowledge on how important holding on to the hope of children in the future is among female AYAs with cancer. Meanwhile, they are frustrated by the rushed decision on fertility preservation at diagnosis. The female AYAs also have existential and ethical concerns related to the choice of cancer therapy and fertility preservation. Finally, they suffer from altered body image, loss of femininity, and body control due to hormone therapy.