A new method, comparative keyword analysis, is used to compare the language of men and women with cancer in 97 research interviews and two popular internet based support groups for people with cancer. The method is suited to the conjoint qualitative and quantitative analysis of differences between large bodies of text, an alternative to the 'code and retrieval' approach used in much thematic analysis of qualitative materials. Web forums are a rich source of data about illness experience and gender differences. Marked differences in the performance of gender are evident. These differences follow linguistic and other behavioural patterns (such as social network differences) established in other contexts. Men with prostate cancer indicate in research interviews that they are more likely to seek information on the internet; women with breast cancer that they are more likely to seek social and emotional support. Men's concerns cluster around treatment information, medical personnel and procedures. Their experience of disease is more localised on particular areas of the body, while women's experience is more holistic. Women's forum postings orientate much more towards the exchange of emotional support, including concern with the impact of illness on a wide range of other people. Women's use of superlatives as well as words referring to feelings indicate their enactment of greater emotional expressivity. Web forums are platforms for an intensification of men's knowledge gathering activities. Web forums, though actually quite publicly visible, appear to be subjectively experienced by both sexes as relatively private places for the exchange of intimate personal information. The 'privacy' of the breast cancer forum facilitated interactions found in other studies to be characteristic of women's friendship groups.