Oncological diseases are today one with highest prevalence diseases. Because of the high mortality rates, they are in the second place, just behind the cardiovascular system diseases. One of the most unpleasant symptoms is the pain, alongside with many other symptoms that can be present. Whether it is acute or chronic pain it is necessary to approach it thoroughly and to determine the cause of this symptom. Adequate access is also a best and complete intervention. The problem of oncological patients is often chronic malignant pain. Inadequate treatment of pain significantly disturbs the quality of life of oncological patients. In order to determine the occurrence of pain and its impact on the quality of life, hypothesis has been put forward: the presence of pain in malignant diseases has a significant impact on the quality of life. The aim of this study was to investigate the perception of pain in patients with malignant diseases, to evaluate the impact of pain on the quality of life, determine whether there are differences in the perception of pain and the estimated impact on the quality of life by age and sex. The research was conducted at Department of Oncology, University Hospital Center ˶Zagreb˝, in Zagreb during February and March 2018. the survey included 100 patients. Standardized questionnaire was used. Particles were studied with regard to the perception of pain in sleep and activity. We tried to perceive differences in the perception of pain with regard to age, sex, and part of the body affected by pain. In contrast to the differences in the study, the relationship between the examined particles was also examined, as well as the effect of the obtained results on the quality of life of the patient. From research we concluded that the existence of pain further disturbs the quality of life of patients suffering from malignant diseases.