Asthma, chronic obstructive pulmonary disease (COPD) and asthma-COPD overlap syndrome (ACOS) significantly affect the patient’s respiratory system, which requires individualised treatment and professional control. During the SARS-CoV-2 pandemic, all respiratory diseases were taken into consideration as risk factors for severe COVID-19. ACE2 and TMPRSS2 genes, which are crucial for SARS-CoV-2 to enter the host cell, have different expression in the occurrence of asthma or COPD. Also, comparing the severity and mortality of patients with coexistence of asthma or COPD and COVID-19, only COPD patients had worse outcomes of COVID-19, and their mortality was significantly higher. Although ACOS is also a potential risk factor for hospitalisation and mortality in COVID-19 patients, the condition still requires further studies. This overview presents the current state of knowledge on the relationship between the diseases mentioned above and COVID-19.