OBJECTIVES: Critically ill children admitted to the pediatric intensive care unit (PICU) often are malnourished. The aim of this study was to determine the role of nutritional status on admission as a predictor of the duration of mechanical ventilation in critically ill children. METHODS: This was a single-center, prospective cohort study, including consecutive children (ages 1 mo to 15 y) admitted to a PICU. Demographic characteristics, clinical characteristics, and nutritional status were recorded and patients were followed up until hospital discharge. Nutritional status was evaluated by anthropometric parameters and malnutrition was considered if the Z-scores for the parameters were =-2. Adjusted Cox's regression analysis was used to determine the association between nutritional status and duration of mechanical ventilation. RESULTS: In all, 72 patients were included. The prevalence of malnutrition was 41.2%, according to height-for-age Z-score, 18.6% according to weight-for-height Z-score, and 22.1% according body mass index-for-age Z-score. Anthropometrical parameters that predicted the duration of mechanical ventilation were weight-for-age (hazard ratio [HR], 2.73; 95% confidence interval [CI], 1.44-5.18); height-for-age (HR, 2.49; 95% CI, 1.44-4.28); and upper arm muscle area-for-age (HR, 5.22; 95% CI, 1.19-22.76). CONCLUSION: Malnutrition, based on a variety of anthropometric variables, was associated with the duration of mechanical ventilation in this cohort of critically ill children. Assessment of nutritional status by anthropometry should be performed on admission to the PICU to allow targeted nutritional rehabilitation for the subset of children with existing malnutrition.