Quality of life (QOL) assessment requires clinically relevant questionnaires that yield accurate data. This study defined measurement properties and the clinical validity of the European Organisation for Research and Treatment of Cancer (EORTC) questionnaire module to assess QOL in oesophageal cancer. The oesophageal module the QLQ-OES24 and core questionnaire, the Quality of Life-Core 30 questionnaire (QLQ-C30) was administered patients undergoing treatment with curative (n=267) or palliative intent (n=224) and second assessments performed 3 months or 3 weeks later respectively. Psychometric tests examined scales and measurement properties of the module. Questionnaires were well accepted, compliance rates were high and less than 2% of items had missing data. Multi-trait scaling analyses and face validity refined the module to four scales and six single items (QLQ-OES18). Selective scales distinguished between clinically distinct groups of patients and demonstrated treatment-induced changes over time. The EORTC QLQ-OES18 demonstrates good psychometric and clinical validity. It is recommended for use with the core questionnaire, the QLQ-C30, to assess QOL in patients with oesophageal cancer.