Introduction: The existence of different reference populations for overweight and obesity diagnosis in children warrants comparative analysis. Objectives: To determine existing differences in nutritional diagnosis using different reference populations. Design: Descriptive, comparative and transversal study. Setting: Hospital Dos de Mayo Growth and Development Section and a Lima Metropolitan State School. Participants: Male and females children aged between 2 and 17 years. Interventions: Two hundred and nineteen children 2 to 5 year-old were studied, as well as 1141 girls and adolescents between 9 to 17 years. In the first group chronic malnutrition (height / age < -2 SD) and obesity (weight/ height > +2 SD) diagnosis was done according to the 1983 National Center for Health Statistics (NCHS) and 2005 World Health Organization (WHO) references. In the second group body mass index (B...