The health status questionnaire Short-Form 36 (SF-36) includes subscales measuring both physical health and mental health. Psychometrically, the mental health subscale contains a mixture of mental symptoms and psychological well-being items, among other things, to prevent a ceiling effect when used in general population studies. Three of the mental health well-being items are also included in the WHO-Five well-being scale. In a Danish general population study, the mental health subscale was compared psychometrically with the WHO-Five in order to evaluate the ceiling effect. Tests for unidimensionality were used in the psychometric analyses, and the sensitivity of the scales in differentiating between changes in self-reported health over the past year has been tested. The results of the study on 9,542 respondents showed that, although the WHO-Five and the mental health subscale were found to be unidimensional, the WHO-Five had a significantly lower ceiling effect than the mental health subscale. The analysis identified the three depression symptoms in the mental health subscale as responsible for the ceiling effect. The WHO-Five was also found to be significantly superior to the mental health subscale in terms of its sensitivity in differentiating between those persons whose health had deteriorated over the past year and those whose health had not. In conclusion, the WHO-Five, which measures psychological well-being, reflects aspects other than just the absence of depressive symptoms.