Background: Life-quality tests are the basis for assessing the condition of oncological patients. They allow for obtaining valuable information from the patients regarding not only the symptoms of disease and adverse effects of the treatment but also assessment of the psychological, social and spiritual aspects. Taking into account assessment of the quality of life made by the patient in the course of disease has a positive effect on the well-being of patients, their families and their caregivers as well as on satisfaction with the interdisciplinary and holistic oncological care. Methods: A population-based, multi-area cross-sectional study was conducted among patients with cancer in the study in order to assess their life quality. The method used in the study was a clinical interview. Quality of life was measured using the EQ-5D-5L Quality of Life Questionnaire, the Karnofsky Performance Status, our own symptom checklist, Edmonton Symptom Assessment and Visual Analogue Scale. Results: In the subjective assessment of fitness, after using the Karnofsky fitness index, it was shown that 28% (95% CI (confidence interval): 27–30) of patients declared the ability to perform normal physical activity. In the assessment the profile, quality of life and psychometric properties of EQ-5D-5L, it was shown that patients had the most severe problems in terms of self-care (81%, 95% CI: 76–89) and feeling anxious and depressed (63%, 95% CI: 60–68). Conclusions: Cancer undoubtedly has a negative impact on the quality of life of patients, which is related to the disease process itself, the treatment used and the duration of the disease.