Two experiments were performed to investigate the effects of text-background lightness difference on visual comfort. A panel of 21 young and 20 older observers in Taiwan participated in Experiment I, using an LCD TV (with a display luminance of 551.8 cd/m(2)) as the presentation media. The results show that on a light background, visual comfort increases as the lightness difference gets larger and larger. On a dark background, however, the highest visual comfort value can be obtained when there is a moderate lightness difference. There seems to be little effect of age on visual comfort using the LCD TV with regard to the lightness difference. In Experiment II, 20 young and 20 older Taiwanese observers participated, using a tablet computer (with a display luminance of 397.3 cd/m(2)). According to the results, the larger text-background lightness difference, the higher visual comfort value for older observers. For young observers, however, the highest visual comfort value can be obtained when there is a moderate, rather than extremely high, lightness difference. These findings can help provide useful guidelines for graphic user interface design in modern e-reading devices. (c) 2014 Wiley Periodicals, Inc. Col Res Appl, 40, 125-134, 2015