There is a broad variety of factors that are contributing to the nursing staff shortage. They include low wages, poor image of nursing, job satisfaction, ageing of the nursing workforce and cost reductions. In the Greek National Health System, there is a policy of open-visiting hours in hospitals. Family members stay with the patients for many hours and provide in-hospital informal care. The purpose of this study is to describe the perceptions of nursing staff about the nursing staff shortage and the in-hospital informal care in a Greek oncology hospital. For the data collection we used a 30-item questionnaire. The majority of the participants (82.9%) stated that most patients have a family member staying longer than the official visiting hours for assisting with care. A main reason according to the nurses' opinion (37.4%) is the nursing staff shortage. In addition, most nurses disagree with relatives providing some of the informal caregiving activities. The findings are consistent with the findings of other studies. They might be of interest to Greek health authorities, to nurses and to Greek citizens in order to implement possible solutions to improve the hospitalization in Greek hospitals.