We report our experience with nasal mask ventilation in children and adolescents with type II respiratory failure admitted to the paediatric intensive care unit (PICU) over an 18-month period. Seven patients were treated with nasal mask ventilation during part of their PICU stay. All showed significant improvement in arterial pH, PaCO2, and PaO2/FiO2 from presentation to discharge, although at discharge PaCO2 and PaO2/FiO2 fell outside of the normal range. Complications occurred in four patients. When compared to 11 patients with type II respiratory failure not treated with nasal mask ventilation, the nasal mask ventilation group had a similar PICU length of stay and incidence of complications. We conclude that nasal mask ventilation may be useful in maintaining near normal alveolar ventilation in selected children with type II respiratory failure and that a prospective study of this technique is indicated.