• Change from baseline in Forced Vital Capacity, Morning Peak Expiratory Flow, Daytime and nighttime asthma symptom scores, beta-agonist use and discontinuation rate [ Time Frame: Week 2, 4 and 8, then at week 12 ]
• Incidence of Adverse Events [ Time Frame: Week 2, 4 and 8, then at week 12 ]
• Pharmacokinetics of budesonide (AUC, maximum concentration and time to maximum concentration [ Time Frame: 6 or 12 hours post dose ]

A comparison of the safety, efficacy and budesonide pharmacokinetics of the currently approved Pulmicort Turbuhaler with a new version of the inhaler, in children and adolescents who have asthma. In addition the study evaluated the functionality of the new inhaler at the end of its intended life.

Inclusion Criteria:

• Male or females aged 6 to 17 with a diagnosis of asthma for at least 3 months. Have used inhaled corticosteroids for no more than one month before entering the study or none at all.
• A forced expiratory volume (FEV1) in 1 second of 75% to 90% of predicted normal for those aged 6 to 11 and 60% to 90% for those aged 12 to 17 years.
• Airway reversibility of at least 12% , use of orally inhaled corticosteroids for no more than one month immediately before entering the study or none at all.

Exclusion Criteria:

• Life threatening asthma, Two or more overnight hospitalisations for asthma within 1 year or any emergency room visit for asthma within 6 months of starting study.
• Use of steroid tablets or injections during the month prior to Visit 1 and use of other asthma medicines (except rescue medication) within 2 weeks prior to the study.
• Any acute exacerbation of asthma or a respiratory tract infection within 30 days prior to Visit 1. Must not smoke or have smoked.