This paper presents the findings of a research project investigating daylighting quality through its perceived effect on the everyday user of a space. The subjects participating in the experiments are asked to describe their perception of the daylit environment through a standard questionnaire. The physical measurements taken in these daylit spaces are then correlated with the subjects’ sensations, in order to identify which quantifiable parameters affect daylighting quality and others which are non quantifiable. The main results suggest that quality is in fact the main criterion by which users judge the daylighting in a space. A new index named LD is derived, which correlates successfully with user responses. The paper concludes by presenting the impact of the findings on daylighting design.