Aims: Assessment of oral and dental problems is seldom routine in clinical oncology, despite the potential negative impact of these problems on nutritional status, social function and quality of life (QoL). The aim was to develop a supplementary module to the European Organisation for Research and Treatment of Cancer Core Questionnaire (EORTC QLQ-C30) focusing on oral health and related QoL issues in all cancer diagnoses. Methods: The module development followed the EORTC guidelines. Phases 1&2 were conducted in France, Germany, Greece, Netherlands, Norway and United Kingdom, while seven countries representing seven languages were included in Phase 3. Results: Eighty-five QoL-items were identified from systematic literature searches. Semi-structured interviews with health-care professionals experienced in oncology and oral/dental care (n = 18) and patients (n = 133) resulted in a provisional module with 41 items. In phase 3 this was further tested in 178 European patients representing different phases of disease and treatment. Results from the interviews, clinical experiences and statistical analyses resulted in the EORTC QLQ-OH17. The module consists of 17 items conceptualised into four multi-item scales (pain/discomfort, xerostomia, eating, information) and three single items related to use of dentures and future worries. Conclusion: This study provides a useful tool intended for use in conjunction with the EORTC QLQ-C30 for assessment of oral and dental problems. The increased awareness may lead to proper interventions, thereby preventing more serious problems and negative impact on QoL. The reliability and validity, the cross-cultural applicability and the psychometric properties of the module will be tested in a larger international study. © 2012 Elsevier Ltd. All rights reserved.