Background : Studies have shown a high risk of interstitial lung disease after hospitalization with adenovirus (AdV) and a high risk of asthma after hospitalization with respiratory syncytial virus (RSV) Objective : To clarify to what extent children hospitalized with respiratory tract infection caused by AdV or RSV develop pulmonary disease Design : Register-based cohort study Methods : Data on infections with AdV and RSV were coupled to data on asthma, asthma medication bronchiectasia, and interstitial lung disease including bronchiolitis obliterans during a follow-up time of 15 – 20 years. An age-matched control group was also generated. The risks of subsequent lung disease and/or having received asthma medication and hazard ratios (HRs) for asthma between the index groups and the control group were computed Findings : In total 4704 children were included. Less than 5 cases of interstitial lung disease or bronchiectasia were found in any group. After hospitalization with AdV or RSV the risk of acquiring an asthma diagnosis or having received asthma medication during follow up was 29% and 65%, respectively for AdV, and 22% and 51%, respectively for RSV; corresponding to adjusted HRs of 2.16 (0.92-5.07), 2.60 (1.57-4.31), 2.87 (2.30-3.58), and 2.37 (2.07-2.71), respectively Conclusion : We could not confirm an increased risk of interstitial lung disease after infection with AdV. However, there is a considerable risk of asthma after hospitalization with AdV or RSV and with respect to RSV the risk is higher than previously reported as expressed by the fraction having received asthma medication during follow up