In a two-group, multi-centre, randomised controlled 9 months trial, we (1) evaluated the impact of a computer-based educational programme compared to standard care and (2) examined whether different patterns of programme usage could be explained by demographic, medical and psychosocial factors. We involved 226 Swedish-speaking women diagnosed with early-stage breast cancer and scheduled for surgery. Primary outcomes were health self-efficacy and health care participation measured by the Comprehensive Health Enhancement Supportive System instrument. Secondary outcomes were anxiety and depression levels measured by the Hospital Anxiety and Depression scale. The Functional Assessment of Cancer Therapy-Breast and Sense of Coherence scales measured psychosocial factors for the study's secondary aim. Multi-level modelling revealed no statistically significant impact of the computer-based educational programme over time on the outcomes. Subsequent exploratory regression analysis revealed that older women with axillary dissection and increased physical well-being were more likely to use the programme. Furthermore, receiving post-operative chemotherapy and increased meaningfulness decreased the likelihood of use. Providing reliable and evidence-based medical and rehabilitation information via a computer-based programme might not be enough to influence multi-dimensional outcomes in women diagnosed with breast cancer. The use of these programmes should be further explored to promote adherence to e-Health supportive interventions.