Aims: With access to the groundbreaking nationwide health administrative data of Singapore (coverage of 4.1m residents), this study aimed to analyse hospitalisation and cost burdens of patients with chronic respiratory diseases over the past 20 years and the impact of COVID-19. Methods: We retrieved individual-level de-identified hospitalisation records of Singaporean residents between 1998-2020 and identified patients with asthma or COPD (primary diagnosis). Using generalized liner models, we estimated the disease- and comorbidity-related admission rates, bed-days and costs for asthma and COPD cohorts between 2000-2020. Change point analysis was used to analyse trends.Results: We analysed 13,656 and 102,694 inpatient episodes from 1,589 and 10,065 asthma and COPD patients. Between 2000-2019, the average annual admission rates for asthma and COPD were 69.1 and 870.5 per 10,000, leading to an annual total of 982 bed-days and $877,911 for asthma (asthma: 29.5% of total costs; other respiratory conditions: 15.7%; others: 54.8%), and 10,713 bed-days and $6,733,476 for COPD (COPD: 30.1% of total costs; cardiovascular: 15.0%; other respiratory conditions: 17.5%; others: 37.4%). Based on the latest stable trend, asthma and COPD admission rates would grow by 0.94%/year (95%CI: 0.90%-1.00%) and 0.85%/year (95%CI: 0.83%-0.88%) into future. In 2020, however, admission rates of asthma and COPD cohorts dropped to 24.0 and 98.3 per 10,000, leading to annual total costs of $677,228 and $1,233,324, respectively. Conclusions: If inpatient volume recovers to pre-pandemic levels, the secondary care burden of patients with chronic respiratory diseases in Singapore are expected to grow significantly.