The aim of this study was to clarify how the characteristics of a lighting environment at nightinfluence psychological impressions. We carried out an experiment in which participants observed images of outdoor scenes at night and evaluated their psychological impressions of the scenes. Results showed that the impression of anxiety was highly correlated with five impressions: brightness, clarity, activity, comfort, and preference.The fact that the impression of brightness had a strong influence on anxiety suggests that brightness is a major factor dominatingthe psychological impression of an outdoor space at night.Analysis of the luminance distribution on the images showed that the impression of brightness was closely correlated with the statistical values representing the intermediate range of luminance distribution on road surfaces but not with the statistics computed from the luminance distribution over the entire area of the images. These results indicate that the impression of the brightness of an outdoor space at night may be determined by the luminance levels covering the wide area of the ground surface.