Introduction: Knowledge of the dangers of sun exposure does not always lead to changes in behavior. Failure to make behavioral adjustments is of particular concern in high-risk patients. Objectives: a) To assess the impact of melanoma diagnosis on knowledge, attitudes, and behaviors relating to sun protection, and b) to identify factors that could influence sun protection behaviors. Methods: A coded, anonymous questionnaire was given to 195 patients with a recent diagnosis of melanoma. Data were collected on clinical and demographic variables and on knowledge, attitudes, and behaviors relating to sun protection before and after diagnosis. The questionnaire also addressed patients sense of distress and guilt following diagnosis. Results: Sun protection behaviors improved following diagnosis in 66% of patients. Although 98% of patients reported having received advice on sun protection following diagnosis, 15% continued to take inadequate sun protection measures. The probability of behavioral improvement following diagnosis was 4 times greater in women than in men. The subgroup of patients whose behavior improved had worse behaviors prior to diagnosis than did those who showed no improvement. Patients who expressed distress and feelings of guilt following diagnosis were more likely to improve their sun protection behavior. Age, tumor site, intensiveness of treatment, and belief that a suntan is healthy had no significant influence on behavioral change. Conclusions: Melanoma diagnosis is associated with increased knowledge of sun protection measures and improvement in behaviors. Nevertheless, patients continue to use inadequate sun protection measures. Identification of barriers to optimal sun protection behavior may be instrumental in designing targeted educational campaigns. (C) 2009 Elsevier Espana, S.L. and AEDV All rights reserved.