Given the aims of this study, the population to be monitored includes adult patients with moderate persistent asthma, which can be defined controlled according to the current guidelines under standard stabilised treatment. The intended treatment duration is therefore designed to ensure that good control of asthma is firmly achieved before stepping down the treatment (8 weeks run-in period), but also that the condition of the patients are followed long enough (24 weeks comparative treatment period) to ensure that a new stable condition is also obtained and properly monitored.