The life expectancy for patients with cystic fibrosis has improved remarkably over the last 20 years. Progressive deterioration of pulmonary function continues despite the aggressive use of antimicrobials. The absence of fever, neutrophilia, and systemic symptoms suggest that during pulmonary exacerbations other non-bacterial factors may have played a part. Some have suggested respiratory viruses as main suspects. So far, few data have illustrated the relationship of respiratory viruses and cystic fibrosis. By gaining further knowledge of this relationship, one may change future clinical practice and boost the survival of these patients.