We investigated the effect of the exposure to daylight and artificial light indoor during Scandinavian winter. Twenty-one subjects experienced two radically different lighting solutions for three days in a row, eight hours each day: one group (n=12) was exposed only to daylight, one (n=9) only to artificial electric lighting (>500lx average on work plane, 3000K). We observed an effect between light conditions on mood, which was elevated in the daylight room. Mean levels of alertness and perceived energy ratings were higher in the daylight condition. An effect of the lighting condition was found for activity levels as measured by the actigraphs, especially in the morning. Due to the experimental design it is at present difficult to tease out if observed effects were due to the lighting exposure or to other environmental factors, e.g. architectural layout, timing or intensity of the exposure, therefore future further studies would be needed to examine different combinations of factors.