The prevalence of seasonal depressive mood, especially among girls, suggests the need for more interventions from schools and health authorities. Results indicated that 25.5 percent of girls and 13.8 percent of boys reported experiencing depression during the winter season. Another 8 percent of students reported severe depressive symptoms. Analysis of the factor structure and internal consistency of the measurement instrument, the Kiddie SPAQ (K-SPAQ), indicated a two-factor structure with good internal consistency. Participants were 756 17- and 18-year-old students enrolled in their second year of senior high in a central district of Sweden who completed the K-SPAQ during January 2003. The analysis focused on assessing the prevalence of self-reported depressive mood during different seasons, gender differences in self-reported seasonal depressive mood, differences between adolescents with and without depressive moods, and the particular symptoms associated with seasonal depressive mood. Tables, figure, references