The European Organisation for Research and Treatment of Cancer (EORTC) Quality of Life Group (QLG) has refined its strategy towards symptom measurement to meet the needs of researchers and clinicians in light of rapidly changing treatment for cancer patients. The standard use of the validated core questionnaire QLQ-C30 together with a disease-specific module can now be complemented by a user-created item list to cover novel side-effects of a tested drug/treatment. Therefore, the EORTC QLG has enhanced functionalities of the Item Library, a repository of over 850 unique items in up to 110 language versions, enabling users to develop their custom-made item list. The aim of the Item Library is to facilitate flexible, timely measurement of symptoms, complementing the use of fully validated quality of life instruments. The new strategy forms part of a larger research initiative in the EORTC QLG. The Item Library is already fully accessible to academic and pharmaceutical industry users. It is also undergoing further validation in order to answer all questions arising from the end users. Through multiple search options (symptoms, keywords, related items), users can identify items and scales that best address the side-effects to be measured. Selected items can then be added to a new questionnaire, including the corresponding conditional items, instructions, response scales and time frames. The finalised custom item list is subsequently reviewed by the Item Library’s content manager, to ensure that the questionnaire is composed correctly and contains all the necessary elements and information. The approved custom questionnaires become available for all other users to browse through, export or adapt for use in their trials, creating an invaluable resource for research and broadening the portfolio of available instruments.