OBJECTIVE: To estimate which (input) factors influence patients' satisfaction of asthma treatment and what impact each factor has on the overall satisfaction. A secondary objective is to look how outcome variables, as compliance/adherence and health-related quality of life (HRQL), and are connected with the overall satisfaction. METHODS: To be able to estimate which factors that are determining patient satisfaction with asthma treatment a questionnaire regarding features of the drug, the physician, the nurse, the availability of the centre, compliance, and health related quality of life was administrated. A total of 599 patients with asthma, aged 18-65 years, from 17 centres in Sweden completed the questionnaire. A Patient Satisfaction Index (PSI) was estimated and each factors impact on the overall satisfaction was analysed. The statistical technique applied for this analysis was Partial Least Squares (PLS), which is well suited for structural equation modelling when the focus is on identifying the most important characteristics. RESULTS: The two most important factors for the patients' overall satisfaction (PSI) of asthma treatment are the drug and the physician (both have a regression coefficient of 1.7). The nurse and the availability of the health centre are, although statistically significant, of less importance. The most important factor for compliance is the drug, where the ease of usage, and absence of side effect was estimated having a higher impact for compliance then the price and the effect of the drug. However, it is interesting to note despite showing a high PSI patients´ still state low HRQL. CONCLUSIONS: The most important factors in the treatment of asthma from the patients point of view are the drug and the physician.