Background: Post-stroke depression affects the outcome of stroke rehabilitation and is observed in approximately 30% of all stroke patients. We investigated whetherthe addition of light treatment to medical antidepressants influences the course of depression as measured by the Hamilton Depression Scale. Methods: The effect of a combination of light therapy and citalopram in stroke victims receiving citalopram was examined by use of two different doses of light therapy under double-blind conditions. Altogether, 63 patients were included in the study. The mean age was 74.9 years. Results: After 4 weeks of therapy, the 6-item subscale of the Hamilton Depression Scale showed a statistically significantly larger improvement in patients receiving high-intensity light treatment compared to those treated with medium-intensity light (p < 0.05). Conclusion: This pilot study demonstrates a dose response effect of light used as an adjunct therapy to antidepressants in post-stroke patients with major depression.