Recent chronobiology research has shown that lighting is important for health and performance. However, most of these studies are performed at night or under unnatural conditions (e.g. after sleep or light deprivation). This symposium discusses the psychological effects of light during daytime. More specifically, this symposium focuses on whether exposure to natural and/or artificial light can improve people's feelings of alertness, vitality and mood, restore their attention and replenish their resources, and enhance cognitive performance during daytime. We start with an overview of current literature investigating lighting effects on performance and mood, and a discussion of the potential benefit of light for attention restoration. Subsequently, an experiment will be presented exploring the effect of the amount and color of white light on ego replenishment and vitality. A preference study investigates whether these alerting and vitalizing effects of light are also reflected in individuals' light preferences. In addition, the potential benefits of exposure to blue light for older people will be discussed in this symposium. Thus, this symposium will present diverse studies investigating the alerting and vitalizing effects of light focusing on psychological mechanisms. Anna Steidle, Alexander Zill, & Lioba Werth. The impact of indoor lighting on human performance and affect: A meta-analysis. Yvonne de Kort, Karin Smolders, & Femke Beute. Lighting and self-regulation: Can light revitalise the depleted ego? Karin Smolders & Yvonne de Kort. How do you like your light in the morning? Preferences for light settings as a function of time, daylight contribution, alertness and mood. Conrad Schmoll, Jenny Roe, Christelle Tendo, Colin Goudie, Peter Aspinall, David McNair & Bal Dhillon. An eye to health: Non-visual effects of blue light for older people.