Obesity and vitamin D deficiency in pediatric populations are two important andprevalent health problems. Obesity is a rising problem and according to literature vitamin D deficiency is more prevalent in obese population being vitamin D status an important point of investigation nowadays as regards its role in cardiovascular diseaseJustification: Recent literature indicate an important role of vitamin D status in cardiovascular disease, in fact there are a large number of in vitro and animal studies which show an important relation between them; however experimental trials have failed to find causalityThis may be explained by different dose regimes, treatment duration or inclusion criteria.Objectives: Study the effect of vitamin D supplementation for one year on cardiovascular risk markers: Blood Pressure (BP), Carotid Intima media thickness (cIMT), Pulse wave velocity (PWV) and C-reactive protein (CPR) in pubertal obese children.Participants: Subjects will be adolescents (10-15 years) with obesity (>95th centile), pubertal development (Tanner 2 or over) and Caucasian ethnicity located in the area of Gironès. 48 subjects will be selected (24 placebo group and 24 vitamin D group) according to inclusion criteria (Body mass index: +2.0 SD and +3.5 SD for age and gender). Vitamin D deficiency status: <12 ng/ml. Free vitamin D < 3.0 ng/ml. Several exclusion criteria are applied also to these subjects. Main outcome measures: Primary outcomes: BP, cIMT, PWV and CPR. Secondary outcomes: glucose, fasting insulin, HOMA, lipid profile and HWM adiponectinIntervention and method: Intervention will be placebo or vitamin D, cholecalciferol (Deltius®) 25.000 IU / two week (equivalent to 1785 IU/day), with a 1:1 ratio and will be stratified by age, gender and BMI. Baseline measurements will include blood pressure, cIMT, PWV and CPR (additional parameters will also be studied). The intervention will last 12 months. The measures will be taken at the beginning, and at 6th and 12th months, being one year the estimated period to carry out this clinical trial.Settings: The study will be performed in Hospital Dr. Josep Trueta (Idibgi).Data analysis: Data analysis will be performed using SPSS version 12.0. Results for major variables will be performed using Mann-Whitney test (Continuous variable) and Fisher exact test (categorical variables). The analysis of response to treatment for endpoints variables (SBP, cIMT, PWV and CRP) will be performed by general lineal model (GLM) for repeated measures. A p value < 0.05 will be considered statistically significant