A study of more than 10,000 female students from 23 countries found they were no better informed about the disease than their male counterparts.
Fewer than 5% realised that alcohol, exercise or being overweight could influence breast cancer risk.
The European Journal of Cancer study was led by Cancer Research UK.
Just over half of those questioned were aware that genes could play a role in influencing breast cancer risk. Awareness of genetic factors was particularly high in the UK and US.
But awareness of the potential significance of lifestyle factors was much lower.
US students were most likely to be aware of their potential influence - but even here ignorance was widespread.
More than 15% of US students identified obesity as a risk factor, compared with under 7% of their English counterparts.
While 10% of US students pinpointed the role of alcohol, the figure in the UK was just 4%.
And 18% of US female students thought exercise had an influence on breast cancer, compared to just 3.5% of English students.
Students in both the UK and US were more likely to rate stress as a significant factor - even though evidence for its effect is much more sketchy.
The study focused on university students because they were likely to be the opinion formers of the future, said Professor Jane Wardle, director of Cancer Research UK's health behaviour unit at University College, London.
"If graduates are not aware of risks, then it is unlikely that anyone else knows."
"It is very worrying that information about being overweight, having a high alcohol intake and taking little physThe results of this study suggest that students could be overestimating the impact of genetic factors and are certainly underestimating the importance of lifestyle factors.
"The danger is that women who do not have relatives with breast cancer may believe that since they have a lower genetic risk they need take no account of lifestyle risks."
Professor John Toy, medical director of Cancer Research UK, said: "The message that lifestyle can influence breast cancer risk is a very important one to get across to all women to enable them to take some control over their future lives."Last Mod: 20 Eylül 2018, 18:16