OBJECTIVES: Quality of life, lung function values, and disease severity classification systems are frequently used in clinical practice, clinical trials and in economic evaluation of asthma treatment. However, the relationship among these measurements is not well understood yet. The objective of this study was to identify quality of life values of asthmatic patients with different severity of disease based on the GINA severity classification system. To examine the correlation between lung function values (FEV1, PEF) and generic and disease-specific QoL measurements. METHODS: 228 consecutive adult outpatients and inpatients at four sites participated in the study. Doctors had to classify the severity of disease and report the latest measured FEV1 and PEF values. Patients had to fill in three different quality of life questionnaires. RESULTS: Mean quality of life values were 21, 38, 52, 60 for SGRQ questionnaire; 48, 43, 36, 31 for SF-36 (PCS); 55, 46, 42, 44 for SF-36 (MCS); 0.93, 0.76, 0.65, 0.52 for EuroQol weighted health status in the four severity groups, respectively. Correlation coefficients were 0.62 between EuroQol and PCS; 0.59 between EuroQol and MCS; -0.74 between SGRQ and PCS; -0.58 between SGRQ and MCS; -0.68 between SGRQ and EuroQol. Correlation was –0.28, 0.37, -0.01, 0.21 between FEV1% and SGRQ, PCS, MCS, and EuroQol, respectively. Similar values were gained in the case of PEF% values. CONCLUSIONS: Lung function and QoL values correlated less than medium strongly while different QoL values correlated to each other stronger than medium. Large differences were detected in QoL according to disease severity. These results can be of high value in modeling and burden of disease studies.