Introduction: Surveillance and monitoring through anthropometric measurements in a specific population is essential to analyze trends and prevalence's of nutritional status. Objective: To determine if the Weight Index (PI) is a better indicator to evaluate the nutritional status with respect to the body mass index (BMI) in adolescents living at moderate altitude in Peru. Methods: A comparative descriptive study was carried out in adolescents living at moderate altitude. 415 adolescents in an age range between 10 to 15.9 years were selected in a non-probabilistic way. Weight, standing height, sitting height and waist circumference (WC) were evaluated. The BMI, PI, waist-height index (ICE) and the state of maturity were calculated by APHV (years of Peak Height Velocity). BMI and PI (low, normal, overweight and obesity) determined the nutritional categories. Results: There were significant differences in both sexes between the mean values of CC and ICE in the four nutritional categories when they were classified by PI (p <0.05). When classified by BMI, there were differences in WC and ICE between the normal, overweight and obesity categories (p <0.05), however, there were no differences between low and normal in both sexes (p> 0.05). In prevalence's, when classified by BMI, the% were lower compared to the PI (underestimate), for example, 7.8% in men and 1.9% in women in the underweight category, while in the normal category it was 16.9% in men and 26% in women. In the overweight and obesity categories, the BMI overestimated the prevalence's compared to the PI, the percentages being 3.2% higher in men and 9.7% in women in the overweight category, while, in the obesity category, the men presented higher percentage in 21.4% and in women 17.8%. Conclusions: The BMI underestimates the prevalence's in the category of low and normal weight, at the same time that it overestimates in the categories of overweight and obesity in adolescents of both sexes. The results suggest that the PI could be a useful and valuable tool to assess the nutritional status of adolescents living in a moderate altitude region of Peru.