This study was designed to shed light on the learning difficulties of diabetic patients. An open-ended questionnaire was sent to 85 health care professionals working in the field of diabetes and nutrition who had been trained in patient education techniques. They were asked to describe the skills that were the easiest to teach patients and those that patients mastered the best, as well as the skills they found hardest to teach patients, those that patients mastered the least and those that gave rise to errors persisting after the patients education was completed. On the whole, the results showed that the educators found it easy to teach techniques: patients mastered procedures well and made few mistakes. In contrast, diabetic patients seem to have problems learning skills, such as insulin dose adjustment, that require complex problem-solving (involving multiple variables). Based on these findings, the authors discuss the notions of learning complexity and the time needed for successful patient education.