Colorectal neoplasms, constitute as the third most common cause of cancer worldwide. Among the treatment options, the ostomy involves the need to use a bag outside the body for disposal of feces. This study sought to understand the cancer patients and ostomates experience and use of bag. From the perspective of qualitative research and existential phenomenological research, we interviewed eight patients, men and women. Using the existential categories of Umwelt (world-physical), Mitwelt (relational-world), Eigenwelt (world-own) and Ueberwelt (unknown world), we found that live-with-a-bag implies changes relations with the body, with others, with himself and transcendence. Men and women have different ways of experiencing the disease. In this sense, it is urgent to return, health services, the extent of being that sick, extending the work beyond the biomedical perspective.