Background: There is documented social inequality in cancer. The health-care system may contribute to health equity by targeting interventions to potentially vulnerable patients who may be at risk of not receiving optimal treatment and care. Aim: This study aimed to develop and pilot test a tool to identify patients who may need additional support. Method: The study took place in a department of palliative medicine and in a team for head and neck cancer within an oncology department. The tool to identify potentially vulnerable patients was developed based on literature reviews and interviews with patients and health-care personnel. It was pilot tested in a six-month period, with subsequent interviews with health-care personnel. Results: In total, 212 consecutive patients referred to the departments were systematically screened with the tool by health-care personnel. Of these, 74 (35%) patients were considered potentially vulnerable. The most frequently reported sign of vulnerability was ‘few supportive relations’ (47% of the vulnerable patients). Most health-care personnel found it relevant to focus systematically on these patients. However, some were concerned that using the tool could prove to be stigmatising and were critical of attributing the vulnerability to the individual. Conclusions: Most patients were considered in need of additional support because they lacked a social network or had difficulties communicating with health-care personnel. Applying a tool to identify potentially vulnerable patients was feasible and increased attention to this group of patients. However, the screening procedure was also questioned.