Compare the Effects of Seretide® Evohaler and a Generic Salmeterol/Fluticasone Hydrofluoroalkane (HFA) Pressurized Metered-dose Inhaler (pMDI) on Functional Respiratory Imaging Parameters in Asthmatic Patients

Inclusion Criteria: * Male or female patient ≥ 18 years old * Written informed consent obtained * Patient with a documented diagnosis of asthma according to the GINA guidelines * Patient with a co-operative attitude and ability to be trained to correctly use the pMDI * Female patient of childbearing potential who confirm that a contraception method was used at least 14 days before visit 1 and will continue to use a contraception method during the study * Patient must be stable and treated in accordance with the GINA guidelines * Patient must be a non-smoker or ex-smoker who have stopped smoking at least 1 year prior to visit 1 and has a smoking history of \< 10 pack years * Patient must be able to understand and complete the protocol requirements, instructions, questionnaires and protocol-stated restrictions Exclusion Criteria: * Pregnant or lactating female * Unstable patient who developed an exacerbation during the last 8 weeks * Patient with upper or lower airways infection * Patient unable to carry out pulmonary function testing * Patient 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 * Patient with cancer or any other chronic disease with poor prognosis and /or affecting patient status * Patient with allergy, sensitivity or intolerance to study drugs and/or study drug formulation ingredients * Patient unlikely to comply with the protocol or unable to understand the nature, scope and possible consequences of the study * Patient who received oral corticosteroids within the last 4 weeks prior to visit 1 * Patient who received any investigational new drug within the last 4 weeks prior to visit 1 or twice the duration of the biological effect of any drug (whichever is longer) * Patient with a history of alcohol or substance abuse that in the opinion of the investigator may be of clinical significance * Patient who has undergone major surgery in the last 12 weeks before the visit 1 or has planned to undergo a major surgery before the end of the trial * Patient with diagnosis of chronic obstructive pulmonary disease (COPD)