Objective: 12,13-Dihydroxy-9Z-octadecenoic acid (12,13-diHOME) is a lipokine secreted from brown adipose tissue, and it has positive effects on dyslipidemia.Acute exercise has been shown to lead to an increase in its secretion. In this study, it was aimed to investigate the relationship of 12,13-diHOME with obesity, exercise and dyslipidaemia for the first time in the adolescent age group.Design: Prospective study.Patients: Twenty-eight male adolescents with obesity and the same number of agematched healthy normal-weight male controls.Measurements: Fasting serum glucose, insulin, lipid and 12,13-diHOME levels were measured. Cardiopulmonary exercise testing was performed in all subjects using a stress test treadmill. Peak oxygen consumption (peak VO2) and anaerobic threshold heart rate (ATHR) were measured.Results: Adolescents with obesity had lower 12,13-diHOME levels than normalweight adolescents both before and after acute exercise (p = .025 and p = .019, respectively), and after acute exercise, 12,13-diHOME levels significantly increased in both groups (p = .001 for both). 12,13-diHOME levels negatively correlated with triglyceride, total cholesterol, LDL-C, and positively correlated with HDL-C. Also, peak VO 2 and ATHR levels showed positive correlation with 12,13-diHOME levels.Conclusion: 12,13-diHOME levels were found to be lower in adolescents with obesity than normal-weight adolescents and increased with acute exercise. Also, the close relationship of this molecule with dyslipidaemia in addition to that with obesity suggests that it has an important role in the pathophysiology of these disorders.Further molecular studies will further elucidate the role of 12,13-diHOME in obesity and dyslipidaemia.