The objective of this study is to evaluate the effect of the combination of formoterol and beclometasone dipropionate in a dry powder inhaler (NEXThaler®) on central and peripheral airway dimensions in asthmatic patients. Therefore Computational Fluid Dynamics (CFD) will be used. Further more, the effect of this combination therapy on lung function (spirometry, resistance and diffusion), the Asthma Control Test (ACT™) and the Asthma Control Questionnaire (ACQ) will be assessed and the safety will be evaluated.

Inclusion Criteria:

1. Patients with moderate asthma as defined by the current GINA guidelines. Patients can belong to 2 categories:

   Group 1 (n=15 to 20, at least 4 current smokers): Patients not well controlled (partially controlled or uncontrolled according to the GINA guidelines) when using medium daily dose of ICS or medium dose ICS + long acting inhaled 2-agonists (LABA) (for definition please refer to the addendum in section 15) given for at least 6 weeks as large-particle formulation (non extra-fine).

   Group 2 (n=15 to 20, at least 4 current smokers ): Patients well controlled (according to GINA guidelines) when using medium daily dose of ICS + LABA (for definition please refer to the addendum in section 15) given for at least 6 weeks as large-particle formulation (non extra-fine).

2. Male or female patients aged ≥18 years

3. Patients with a documented diagnosis of asthma according to the GINA guidelines

4. Patients with a co-operative attitude and ability to be trained to correctly use the Foster NEXThaler DPI

5. Written informed consent obtained

Exclusion Criteria:

1. Patients treated with extra-fine ICS either alone or with LABA
2. Pregnant or lactating females or females at risk of pregnancy at screening and not willing to use an appropriate contraception method during the study period
3. Inability to carry out pulmonary function testing
4. History of near fatal asthma
5. Hospitalization due to asthma or symptomatic infection of the airways in the previous 8 weeks
6. Patients with an uncontrolled disease or any condition that might, in the judgement of the investigator, place the patient at undue risk or potentially compromise the results or interpretation of the study
7. Cancer
8. Current alcohol or drug abuse
9. Allergy, sensitivity or intolerance to study drugs and/or study drug formulation ingredients
10. Patients unlikely to comply with the protocol or unable to understand the nature, scope and possible consequences of the study
11. Patients who received any investigational new drug within the last 4 weeks prior to the screening visit
12. Patients treated with any non-permitted concomitant medication