Self-reported short or long sleep duration has been repeatedly found to be associated with increased mortality and health risks. However, there is still an insufficient amount of detailed knowledge available to characterize the short and long sleep duration groups in general population. Consequently, the underlying mechanisms potentially explaining the health risks associated with short and long sleep duration are unclear. In the present study, the self-reported sleep duration in a sample of Finnish general population was studied, and its possible associations with such factors as self-perceived health, sociodemographic characteristics, lifestyle, sleep difficulties and daytime concomitants were analyzed. In particular, an effort was made to define mutually statistically-independent determinants of sleep duration. In the Finnish Health 2000 Survey, a representative sample of 8,028 subjects of 30 years of age or older and a sample of 1,894 subjects of 18-29 years of age were invited to take part in the health interview and health examination. The participation rate of the study was over 80%. The most important and statistically-independent determinants of short and long sleep duration were gender, physical tiredness, sleep problems, marital status, main occupation and physical activity. However, in the multivariable model they only accounted for approximately 16% of the variance in sleep duration in short and long sleepers, suggesting multiple sources of variance. The present study also suggests a dose-response like relationship between the sleep duration and many of its determinants within both short and long sleepers. A more detailed analysis of the clinical status of the short and long sleep duration groups is needed to evaluate the possible importance of these findings for health risks associated with sleep duration.