Background: The aim of this study is to evaluate the presence of anxiety, depressive and adjustment disorders, suicide ideation, and symptoms of anxiety and depression in patients with cancer before (T1), and after radiotherapy (12) and at the 1-month follow-up (T3). Methods: A longitudinal study on 103 patients with cancer treated as outpatients undergoing radiotherapy was carried out, evaluating them three times (T1-T2-T3) according to DSM-IV criteria with the Mini-International Neuropsychiatric Interview and the Hospital Anxiety and Depression Scale. Results: Prevalence of the depressive disorders was: T1 = 6.8%, T2 = 3.9% and T3 = 3.9%; for anxiety disorders: T1 = 16.5%, T2 = 18.4% and T3 = 16.5%; for adjustment disorder: 10.7%, 5.8% and 7.8%; and for suicide ideation: T1 = 11.7%, T2 = 7.8% and T3 = 7.8%. In all, the presence of disorders was: T1 = 35%, T2 = 26.2%0.4% and T3 = 29.1%. At least one mental disorder was diagnosed in 46.6% of patients in one of the three times of the study. In relation to the symptoms, the prevalence of the possible cases of clinical anxiety was: T1 = 35.9%, 12 = 18.4% and T3 = 22.3%; the prevalence of possible cases of clinical depression was 19.4%, 16.5% and 10.7%, respectively; and the prevalence of emotional distress was 27.2%, 17.5% and 18.4%, respectively. All symptoms decreased significantly from T1 to 12 and from T1 to T3, with moderate effect sizes. No changes were observed between the end of the radiotherapy and the follow-up period. Conclusions: High prevalence of mental disorders and symptoms of anxiety, depression and distress were observed in the patients with cancer before finishing radiotherapy treatment and during the follow-up. Funding: Basurto University Hospital and Basque Foundation for Innovation and Research in Health-BIOEF. (C) 2016 Elsevier Inc. All rights reserved.