Every year medical researchers make contact with a large number of cancer survivors with the aim of evaluating cancer treatment. For this reason we decided to investigate how Swedish cancer survivors perceived their participation in research studies focusing on the long-term consequences of being a survivor of gynaecological or urinary bladder cancer. Data were collected by means of two study-specific postal questionnaires, both consisting of questions covering physical symptoms, well-being and the experience of being a cancer survivor. Both questionnaires also included questions evaluating the participants' experience of being research subjects. The questionnaires were developed in close co-operation with cancer survivors. The study population consisted of 1068 cancer survivors. Of these, 95% (n=1003) reported that they thought the study was valuable and 54% (n=559) that they had been positively affected by participating. Four per cent (n=39) expressed that they had been negatively affected by their participation in the study. The vast majority of the cancer survivors thought that participating in their particular study was valuable.