Introduction. Head and neck cancer (HNC) is a global epidemiological and clinical problem. In 2020, it was the seventh most common type of cancer worldwide. In 2019, HNC was the fourth most common cause of cancer death among men in Poland. Radiotherapy plays an important role in the treatment of patients with HNC at all clinical stages. However, it is associated with a significant rate of early and late adverse effects. As head and neck cancers are located close to vital anatomical structures, both the local progression of the disease and the treatments used can cause serious problems for patients with HNC, reducing their health-related quality of life (HRQoL) as well as increasing the risk of depressive disorders. Despite this, the current literature lacks research on these aspects of the therapeutic process in the Polish population. The aim of this study was to assess the early impact of radiotherapy on HRQoL outcomes, psychological distress, nutritional status, and overall performance of patients with HNC. Methods. The study was carried out among 85 patients with HNC treated in the Inpatient Radiotherapy Unit of the Radiotherapy Department of the Lower Silesian Oncology Center in Wrocław. The patients were asked to complete a set of questionnaires, including the EORTC QLQ-H&N35, the BDI, the NRS-2002, and the ECOG scale, at two time points: before the initiation of radiotherapy treatment and after a course of radiotherapy. The period between the assessments was 7 to 8 weeks. Results. Our findings demonstrated a negative impact of radiotherapy on scores in all the cancer-specific symptom and functioning scales used in the study. As regards functioning scales, the largest differences were observed for senses and swallowing, whereas with symptoms scales, the largest differences were noted for “sticky saliva” and “dry mouth”. Over half of the patients included in the study required nutritional support after radiotherapy treatment. We found statistically significant differences in the levels of depressive symptom severity before and after radiotherapy treatment. Conclusion. The present study showed significant changes in the physical and psychological functioning and nutritional status of the patients with HNC studied after radiotherapy treatment, which may have an impact on the effectiveness of cancer treatment.