Patients with head and neck cancer report several disease- and health-related problems before, during and a long time after completed treatment. Nurses have an important role in educating/supporting these patients about/through the disease and treatment so that they can attain well-being. This study describes the cancer patients' experiences of nurses' behaviour in terms of critical incidents after nurses had given them care to promote health. The study had a qualitative, descriptive design and the method used was the critical incident technique. Twenty-one informants from the Nordic countries diagnosed with head and neck cancer were strategically selected. It was explained to the informants what a critical incident implies before the interviews took place; this was defined as a major event of great importance, an incident, which the informants still remember, due to its great importance for the outcome of their health and well-being. The nurses' behaviour was examined, and critical incidents were involved in 208 cases-150 positive and 58 negative ones-the number of incidents varying between three and 20 per informant. The nurses' health promotion activities or lack of such activities based on the patients' disease, treatment and symptoms, consisted of informing and instructing the patients as well as enabling their participation. Personal consideration and the nurses' cognisance, knowledge, competence, solicitude, demeanour and statements of understanding were found to be important. Continuous health promotion nursing interventions were of considerable value for the majority of this group of cancer patients. Oncology nurses could reconfirm and update the care of head and neck cancer patients by including health promotion activities in individual care plans. By more frequent use of health promotion models, such as the empowerment model, the nurses could identify and focus on those individuals who needed to alter their life-style as well as tailor their approach towards these patient by setting goals for well-being and a healthy life-style.