INTRODUCTION Comprehensive symptom assessment may be achieved by combining patient-reported outcome instruments with open-ended questions. The open-ended "Write In three Symptoms/Problems" (WISP) instrument allows patients to report symptoms and problems (S/Ps) not covered by the EORTC QLQ-C15-PAL. This study investigated whether sociodemographic or clinical variables were associated with the reporting of additional S/Ps on WISP. METHODS Data from the Danish Palliative Care Database included all patients admitted to specialist palliative care in Denmark in 2016 who completed the EORTC QLQ-C15-PAL. The associations between patient characteristics and the reporting of a) any additional symptom/problem and b) each of the ten most prevalent additional S/Ps (oedema, dizziness, cough, sweats, diarrhoea, dry mouth, incontinence, sore mouth, vomiting and dysphagia) were investigated using multiple logistic regression. RESULTS In total, 1,295 patients reported additional S/Ps on WISP. Reporting any additional symptom/problem was associated with having younger children and living with someone. The reporting of the most prevalent additional S/Ps was associated with cancer diagnosis, having younger children, living with someone and being an outpatient. CONCLUSIONS This study gives new insights into the characteristics of patients reporting S/Ps that are not assessed by standard measures. The results may assist clinicians in improving palliative care. FUNDING: The salary of the first author was financed by Becas Chile-CONICYT. TRIAL REGISTRATION not relevant.