Objective Sleep duration may contribute to metabolic risks. U-shaped pattern have been observed in the relationships between sleep duration and mortality, cardiovascular disease, diabetes and hypertension. The aim of this study was to investigate the association between sleep duration and metabolic syndrome (MS) in young Korean women. Methods We recruited 2,950 young women (15~39yrs). Detailed questionnaire including demographic information, lifestyle habits and sleep duration were completed. Anthropometric measurements and metabolic parameters were determined. Subjects were classified into 3 groups according to their sleep duration: short (< 6hr, n = 234), normal (6-8hr, n = 1,639) and long sleeper ( > 8hr, n = 1,077). Results Short sleepers were younger and more obese than normal or long sleepers. In long sleepers, post loading 2hr glucose, fasting insulin, triglycerides levels were higher and insulin sensitivity index, HDL cholesterol were lower than normal sleepers (P < 0.05). Long sleepers were significantly associated with metabolic syndrome (OR = 1.706, 95% CI: 1.105-2.632) after adjusting for age and BMI, but not in short sleepers (OR 1.201, 95% CI:0.586-2.463). The prevalence of MS (7.3, 4.3 and 7.0% in short, normal and long sleepers), central obesity (26.9, 16.9 and 19.8%), high triglycerides (5.6, 3.9, 6.9%) and low HDL cholesterol (47.6, 46.9 and 53.4%) was significantly different among these 3 groups (P < 0.05). Conclusion In young Korean women, long sleep duration was significantly associated with MS and also high triglycerides and low HDL cholesterol levels.