We studied the success and success factors of online support groups (OSGs) for patients, and the motives and goals of people who start such groups. We interviewed 23 webmasters of OSGs for patients with breast cancer, fibromyalgia and arthritis. The majority were women (n = 20) and most were patients (n = 21). Analysis of the interviews revealed that webmasters had altruistic and intrinsic motives for initiating an online support group. They defined success as the fulfilment of the goals they had in mind when they initiated their groups. To be able to make a group successful, decisions about its organization and management need to be coherent with these goals. Most webmasters stressed that promoting the group, keeping it alive and moderating the messages were vital success factors during the evolution stage. Management of the OSGs took up much of the webmasters' time and energy. On average webmasters were occupied with the group for 10–15 hours a week. Our study provides an overview of the pros and cons of differing decisions that have to be made when initiating an OSG.