Leukotrienes were found to be raised in respiratory syncytial virus bronchiolitis. Montelukast is a cysteinyl leukotrienes antagonist. We report our experience with the use of montelukast in three young children from 5-months to 20-months old. The first case was a 5-month-old boy with previous good health. He had prolonged respiratory distress secondary to adenovirus type 3 infection. The second case was a 20-month-old boy with bronchopulmonary dysplasia. He had respiratory syncytial virus and an adenovirus type 3 infection leading to prolonged wheeze. The third case was a 20-month-old girl with chronic lung disorder after an episode of severe E. coli pneumonia at 1 month old. She developed acute virus-negative severe wheeze after a few days of running nose and low-grade fever. All three cases responded poorly to inhaled steroids and bronchodilators. Addition of montelukast was associated with marked clinical improvement within 1 week. The three cases were very heterogeneous and differed from usual simple virus-induced acute bronchiolitis. The use of multiple drugs including montelukast did not enable any definite conclusions; however, the addition of montelukast was closely related to clinical improvement. Further studies in the use of montelukast in severe virus-induced bronchiolitis are warranted.