The aim of the study is to investigate the efficacy of ciclesonide versus budesonide on lung function, symptoms and use of rescue medication in patients with asthma. Ciclesonide and budesonide will be inhaled once daily at one dose level each. The study duration consists of a baseline period (1 to 4 weeks) and a treatment period (12 weeks). The study will provide further data on safety and tolerability of ciclesonide.