Background: Studies comparing the efficacy of dawn simulation to conventional bright light for the treatment of seasonal affective disorder (in parallel groups) have yielded conflicting results. This crossover study investigated treatment outcomes and long-term treatment preference. Methods: Forty winter depressives were treated for a week with bright light (4.300 lx for 30-45 min shortly after awakening) or dawn simulation (gradually increasing light during the last 30 min of sleep achieving 100 lx before alarm beep, with the dawn simulator placed closer to the open eyes for a further 15 min: 250 lx). The depression level was self-rated using SIGH-SAD-SR. Results: Depression scores reduced similarly following bright light and dawn simulation: for 43.8% and 42.2% (medians), respectively; efficacy ratio was 23:17. The preference was also similar (21:19). Among those who preferred bright light, the most common reason was that they perceived the bright light to be more effective (19/21; it was more effective, p=0.0096; this subgroup tended to have more severe depression) and ease of use (6/21). Among those who preferred the dawn simulator, the reasons were a more "natural" action (9/19), device compactness and/or Lime-saving (10/19) and in 4 cases where bright light caused eyestrain. Limitations: Not overhead naturalistic light for dawn simulation, self-rating of depression. Conclusions: Dawn simulation is similarly effective to bright light in the treatment of winter depression. Patients with more severe depression tended to report greater improvement with bright light; in such cases, this would outweigh the non-clinical advantages of dawn simulation. (C) 2015 Elsevier B.V. All rights reserved.