Lighting is one of the largest energy users in artificially lit buildings. In this context, daylighting strategies that potentially reduce the needs of artificial lighting have been highlighted. However, they have not always materialized in practice, which is mainly due to the lack of understanding of occupant perception and behaviour of natural and artificial lighting systems. This study reports survey results from a monitoring campaign of four offices in Korea, which was conducted from February to June 2010 with an aim to reveal occupancy patterns, occupant use of lighting systems, and resulting lighting energy use. The results indicate that there are no statistically significant relationships between external illuminance and lighting use patterns, but there is a clear time of day effects (i.e. a strong tendency of turning on lighting on worker's first arrival in the morning). It has been found that the application of automatic dimming control for lighting with a design illuminance of 500 lx demands to the field studied offices can reduce lighting energy consumption by up to 43%. The study also shows that a change in occupancy patterns observed in this study leads to an increase in lighting energy use by up to 50%. (c) 2011 Elsevier B.V. All rights reserved.