Chronic respiratory diseases are determined by genetic predisposition, and environmental and socioeconomic variables. One genetic factor underlying susceptibility to such diseases can be the ABO blood group system. The purpose of this study was to investigate the hypothesis that there would be a relationship between the blood group and risk of developing asthma and chronic obstructive pulmonary disease (COPD). We reviewed medical history files of patients with the diagnosis of COPD or asthma, including those suffering from a cancerous disease accompanied by asthma or COPD, hospitalized from January 2016 to July 2017. The study involved 248 adult patients (85 women and 163 men; median age 65, range 20-95 years) with COPD (177; 71.4%) and asthma (71; 28.6%) with a known blood type. We found that the most frequent was blood type A (97; 39.1%) and the least blood type AB (26; 8.0%). The distribution of individual blood types in asthma was not different from that in COPD patients. Significant differences were found between the distribution of O and pooled non-O blood types (A, B, and AB); the pooled category was more frequent in both asthma and COPD patients. We conclude that the blood type is not a prognostic differentiating between the occurrence of asthma or COPD, although both are less common in people with blood type O. Further investigation is required to set the predisposing role of the ABO antigens for chronic respiratory diseases.