QOLID is a new and comprehensive database in the field of patient reported outcomes (PROs), which is dedicated to all those involved in the evaluation of health outcomes. Its aim is to help researchers to find relevant and reliable information on PRO instruments in an easy and practical way available to all of them. QOLID has been created from a close collaboration between the Information Resources Centre of Mapi Research Institute, Lyon, France and Marcello Tamburini, Istituto Nazionale Tumori, Milan, Italy.