Background: Use of the Internet within a healthcare context offers possibilities, not only to provide information, but also to establish support online. Internet Support Groups (ISGs) are often used by patients with cancer or depression, offering potentials and advantages not provided by face-to-face support. Use of an ISG could be beneficial in patients undergoing lumbar spine fusion (LSF), accommodating isolation after surgery, providing a sense of social life, and contributing to the overall health-related quality of life providing peer support. However, research indicates that LSF patients are often not Internet users, as they often belong to the low-income group, have low education, and are of older age. However, knowledge of LSF patients' use of ISG is limited. Objective: This study describes and analyses the use of an ISG in Danish patients undergoing instrumented LSF due to degenerative spine disorders. Method: A prospective, randomized controlled trial of 114 patients, half of whom were randomized to receive access to an ISG and half to a control group with no access. This study is a prospective cohort where the population comprised those patients randomized to access the ISG (n=57). Sociodemographic characteristics (gender, age, marital status, employment status, and level of education) and information on psychological wellbeing (symptom of anxiety and depression) were obtained at baseline, 1-5 weeks prior to surgery, and the use of the ISG was registered from baseline until 3 months after surgery. Results: Eight participants were excluded. Thus, 49 participants comprised the study population, with a mean age of 53 years (range 29-77), 57% female, 84% not living alone, 70% unemployed, and the majority (69%) had secondary education as their highest education. Approximately one-third of the participants had symptoms of depression (33%), and one-third had symptoms of anxiety (31%), half of these overlapped, having both anxiety and depression. A total of 43 of the 49 participants (88%) took the opportunity to access the ISG. We found no correlations between sociodemographic data and the degree to which participants accessed the ISG. Women were more prone to be active users (P=0.04) and more often contributed with posts to the ISG. Finally, participants who were active users and contributed with posts or comments had more interactions (P<0.001) and pageviews (P<0.001). Conclusions: Sociodemographic characteristics were not predictors of ISG use in this study.