['The aim of this paper was to investigate the relationship between circulating 25-hydroxyvitamin D (25(OH)D) and cardio-metabolic risk factors in a large cohort of obese youth attending tertiary paediatric obesity services.', 'We conducted a retrospective cross-sectional study. Data were retrospectively collected from all new consultations of children and adolescents attending obesity outpatient clinics between 2008 and 2011 at the two major paediatric hospitals in Melbourne, Australia. Information collected included demographics, anthropometry, blood pressure, pubertal staging, body composition and fasting serum levels of 25(OH)D, glucose, insulin, cholesterol, triglyceride, high-density lipoprotein, liver function, calcium and phosphate.', '25(OH)D data were available in 229 patients (age 3-18 years; 116 men; mean (standard deviation) body mass index ( BMI) Z-score 2.5 (0.5)\u2009). One hundred four (45%) participants were 25(OH)D deficient (<50\u2009nmol/L). Lower serum 25(OH)D levels were associated with higher BMI Z-score (P-trend = 0.001), total fat mass (P-trend = 0.009), systolic (P-trend = 0.03) and diastolic blood pressures(P-trend = 0.009). In multivariable-adjusted regression analysis, 25(OH)D was significantly lower in those with elevated blood pressure after adjustment for BMI(P-trend = 0.004) or total fat mass (P-trend = 0.01).'] Is low vitamin D associated with hypertension in paediatric obesity?