Non-invasive ventilation (NIV) is being increasingly used in children with acute respiratory failure, preventing complications associated with conventional mecánical ventilation.To determinate the efficacy of NIV in children with acute respiratory failure or chronic respiratory failure.Prospective study of all patients who underwent NIV (November 2005 to April 2008). Demographic data and the following parameters were analysed: Heart and respiratory rate, SaO2, blood gases evaluated before and at 1, 2, 6, 12, and 24 hours after NIV.One hundred and thirteen were included (116 NIV trials). Mean age 9,4 +/- 26,2 months (median: 1,5 months). CPAP used in 63 and BiPAP in 53 trials.bronchiolitis in 61 (52,6%), pneumonia in 36 (31,0%) patients. Indications for NIV: acute hypercapnic and/or hypoxemic respiratory failure in 109 (94%), apnoea (13), chronic pulmonary disease agudization (three), partial obstruction of upper airway (four). There was a significant improvement in respiratory and heart rates, pH, pCO2 at 1, 2, 4, 6, 12, 24 and 48 hours after NIV onset (p < 0,05) (table). Mean duration of NIV was 47,7 +/- 35,6 hours. Sedation with chloral hydrate was used in 58 (50%). Twenty eight patients (24,1%), required conventional mechanical ventilation (main reason: apnea+bradicárdia: 8). There were no major complications related with NIV.NIV can be effective in children and infants with acute respiratory failure, preventing some patients from deteriorating and/or from being ventilated.