Today, hospitals offer surgical treatment within a short hospital admission. This brief interaction may challenge the well-being of old patients. The aim of this study was to explore how the well-being of old hospitalized patients was affected by the interaction with staff during a fast-track surgical treatment and hospital admission for colon cancer. We used an ethnographic methodology with field observations and unstructured interviews focusing on one patient at a time (n=9) during a full day; the hours ranging from 7:45 a.m. to 8 p.m. Participants were between 74 and 85 years of age and of both sexes. The study was reported to the Danish Data Protection Agency with reference number (2007-58-0010). The encounter between old patients and the staff was a main theme in our findings elucidating a number of care challenges. The identified care challenges illustrated “well-being as a matter of different perspectives,” “vulnerability in contrast to well-being,” and “staff mix influencing the care encounter.” The experience of well-being in old cancer patients during hospital admission was absent or challenged when staff did not acknowledge their individual vulnerability and needs.