Introduction: The level of gratitude may explain the increase in psychological well-being. Some studies demonstrated also the mediating effect of social support for the relationship of gratitude to well-being. The aim of the research was to present the role of the sense of social support and gratitude for the quality of life of patients. It was hypothesized that social support mediates the relationship between gratitude and the quality of life in the group of oncological patients with a moderating effect of gender. Material and methods: The participants comprised 96 Polish cancer patients, with breast or prostate cancer, hospitalized during 5-7 weeks of radiotherapy, and aged 31-79 years. A gratitude questionnaire, the social support scale by Kmiecik-Baran, and the sense of quality of life questionnaire by Stras-Romanowska et al. were used [1]. Results: Social support has not proven to be a mediator of the relationship of gratitude to any dimension of quality of life. However, gender turned out to be a moderator in terms of the relationship between gratitude and instrumental support for the global, psychosocial, and subjective quality of life, but only in women. Conclusions: Gender also turned out to be a moderator of the instrumental support relationship with the global, psychosocial, and subjective sphere of quality of life, and this relationship was found only in men. There was also moderation in the emotional support relationship with psycho social quality of life in the group of men.