INTRODUCTION: One of the complications associated with obesity is nonalcoholic fatty liver disease (NAFLD), which is defined as an excessive accumulation of fat in hepatocytes, and is characterized by chronic elevation of aminotransferases and ultrasonographic abnormalities (increased echogenicity). In the USA it is now the most common liver disease. Prevalence is around 15-25% in the general population, and this increases to 57.5-75% in obese people. The aim of this study was to evaluate whether hepatic steatosis is a factor associated with the presence of metabolic risk in children and obese adolescents. MATERIALS AND METHODS: A retro- and perspective cross-sectional study in the High Specialty Medical Unit No. 25 of the Mexican Social Security Institute in Monterrey, Nuevo Leon, Mexico, in which the clinical records of patients from 5 to 15 years of age, referred with a diagnosis of obesity, were reviewed in the period of January 1, 2012 to June 30, 2013. Children and adolescent patients diagnosed with obesity were included, but we excluded patients with a history of acute and chronic viral hepatitis and use of antiepileptic and hepatotoxic drugs. For descriptive analysis we used absolute frequencies, percentages, means, and standard deviations. For inferential analysis we used chi-square test, Fisher exact test, and Student t test to establish the association of NAFLD with the studied variables. The odds ratio was measured, considering 95% CI and statistical significance p < 0.05. RESULTS: 160 children and adolescent patients were included with median age 11.23 ± 2.2 years, of which 85 (53.1%) were male and 75 (46.9%) were female. All were obese, with BMI and abdominal circumference greater than the 95th percentile for age. In total, 131 (81.8%) patients had NAFLD and 29 (18.2 %) patients did not. HOMA index was increased by 3.9 ± 2.1 (p < 0.05) in patients in the NAFLD group with a mean of 6.4 ± 4.9 in the group without NAFLD. The cutoff point we found for insulin resistance associated with NAFLD was 9. We found four subjects with high LDL levels of (> 130), and none in the control group. Transaminase levels were significantly higher in the group of patients with NAFLD, ALT greater than 40 U/l in 127 (96.94%) of patients with NAFLD (OR: 63.5; 95% CI: 18.5-217; p < 0.005). LDL-C greater than 130 mg/dl occurred in four (3%) patients with NAFLD, and in none of the patients without NAFLD (p = 0.0001). Acanthosis nigricans was found in 128 (97.7%) patients with NAFLD and in only one (3.4 %) in the group without NAFLD (OR: 1194.7; 95% CI: 119.8-1191.5; p = 0.0001). CONCLUSION: Obesity and insulin resistance are risk factors for the development of fatty liver in children and adolescents.