The political or ecological concept of quality of life refers to irreplaceable aspects of life. The health-related quality of life concept has the same impact of considering the irreplaceable (idiographic) aspects of treatment outcome in patients with chronic disorders. When comparing the different attempts to measure quality of life, two main approaches have been considered, namely a multidimensional view of medical disorders and a global view of outcome of treatment. Both approaches have been discussed at the same level of measurement, i.e. how the patient considers the various components. A dialectic procedure has been followed: quality of life data versus ‘raw’ health data; idiographic versus nomothetic scales; index versus profile statistics; generic versus disease-specific measurements.