This Group aims to better understand the effects of cancer and treatment on health-related quality of life for patients across diverse population groups and cultures. Members develop and refine related questionnaires for oncology clinical trials, other well-designed research studies and clinical practice. They also collaborate with other EORTC research groups to implement studies in clinical trials. EORTC’s QLQ-30 questionnaire which has become one of the standard tools to measure quality of life in cancer clinical trials. The core questionnaire, currently available in over 100 languages, is accompanied by more than 20 fully-validated modules, addressing disease or population-specific concerns.