BACKGROUND: The objective of this study was to expand the knowledge on the prevalence of self-reported Seasonal Affective Disorder (SAD) and to further study the validity of the Seasonal Pattern Assessment Questionnaire (SPAQ). METHODS: A total of N=844 young adults were assessed in a Swiss community study by use of the SPAQ, a Seasonal Affective Disorders Questionnaire (SADQ), the Young Adult Self Report (YASR), the Centre for Epidemiologic Depression Scale (CES-D), and scales for measuring self-esteem, self-awareness and life events. At a second stage, a total of N=534 screen positives and controls were subjected to the Composite International Diagnostic Interview (M-CIDI) for the assessment of mental disorders. According to the SPAQ classification a group of SAD subjects and a group of subsyndromal SAD subjects (S-SAD) were defined. In addition, a third group of high-scoring depressives (HSD) subjects scoring above the 75th percentile of the CES-D was defined. Comparisons included these three groups and the rest of the sample serving as controls. RESULTS: The weighted prevalence for SAD in this sample was 7.84% based on the SPAQ alone. With the addition of the SADQ, weighted prevalence rates dropped to 2.22%. Weighted subsyndromal SAD was 33.04%. Across the vast majority of scales, the SAD group was indistinguishable from the HSD group. These two groups scored highest, whereas the S-SAD group had an intermediate position and the controls had the lowest scores. SAD was best predicted by the CES-D total score. CONCLUSIONS: The SPAQ as a single measure leads to an overestimation of SAD which, nevertheless, is a rather common phenomenon also in this central European population. The findings on the validity of the SPAQ are extended by showing that predominantly general aspects of depression are measured.