Research governance requires patients give informed consent to participate in clinical trials. However, there are concerns that consent information may not support patient participation decisions. This study investigates the utility of consent information in supporting women’s trial participation decisions when receiving treatment for cancer. An interview study with women receiving cancer treatments at a medical oncology outpatient clinic in Yorkshire (UK). All women over 18 years, not admitted to a hospital ward and who had currently or previously been invited to take part in a trial were invited to take part in the study over a three month period. Interviews were audio-tape recorded, transcribed and analysed using thematic analysis. Of those eligible (n = 41), 21 women with breast (n = 11), ovarian (n = 8) and endometrial (n = 2) cancer participated (mean age = 57 years). Eighteen had made at least one trial decision and three were considering taking part in a trial. Findings are synthesised under two analytical themes: 1) Influence of the cancer and cancer treatment context on decision making for trial participation; and 2) Experiences of the consenting process and their influence on decision making. Designing trial information to represent explicitly the trial participation decision as being between standard care and study-related care options is more likely to effectively support patients in making informed decisions between standard care treatments and taking part in a trial. •We focus on adequacy of consent information in enabling informed trial decisions.•Choices were made in context of illness management, not ‘research participation’ alone.•There was little evidence of active reasoning between trial participation and standard care.•Trial information should support informed decision between trial participation and standard care.