This study aimed to examine the effect of CCTs on the focused and sustained attention. There are several noteworthy limitations of this study. First, although the study found significant statistical relationships that the 4300 K condition is better in relation with the focused and sustained attention measured by the Chu Attention Test, the study did not provide concrete explanations of the biological or subjective mechanisms underlying such relationships. Further studies are needed to investigate the mechanisms that link CCTs and attention. Second, the study was conducted during the day time from August to November 2012 without particular control of the humidity, noise, or time of the experimental settings. In addition, the study relied on the subjects’ selfreported perceptions of clarity and comfortableness on the lighting condition. Although the relatively large sample size and the random process may mitigate the effects of those uncontrolled factors and the possible self-reported bias, their influence cannot be fully discounted. Third, the study chose the Chu Attention Test to assess the focused and sustained attention. The findings of the study are limited to the use of the specific measurement tool. Using multiple tools to examine the relationships between CCTs and attention may improve the convergent validity of the study.