BACKGROUND: Montelukast (Singulair) is a cysteinyl leukotriene receptor antagonist, used for the maintenance treatment of asthma and to relieve symptoms of seasonal allergic rhinitis and asthma, also used for exercise-induced bronchospasm. AIM: This study was performed to determine the prevalence of Montelukast use as an add-on therapy among Iraqi asthmatic patients on treatment. Comparing the effectiveness of regimens with and without montelukast. METHODS: This descriptive cross-sectional study was carried out on 73 Iraqi asthmatic patients on treatment of both sexes with age range (18-60) years old, attending Al-Kindy Teaching Hospital and Al-Zahraa Centre of Asthma and Allergy, Baghdad, for the period between February and March 2017. A questionnaire was specifically prepared to meet the objectives and was used to collect the data of the study. RESULTS: There was a significant statistical reduction of frequency in asthmatic attacks after Montelukast treatment (p-value < 0.05). Out of 73 patients, 39 were males, and 34 were females, 46 were jobless, 37 were married, 63 were urban residents, 63 were educated. Prevalence of exacerbation factors was as following: infection was found in 60.3% of the patients, exercise in 57.5%, dust in 72.6%, smoking in 60.6%, food in 24.7%, others (stress, perfumes) in 20.5%. The prevalence of Montelukast use in this study was 46% (34 patients). Out of 34 patients using Montelukast, 28 were using inhaled salbutamol, 5 were using oral salbutamol, 15 were using inhaled corticosteroids, 9 were using systematic corticosteroids, 2 were using xanthines, and 6 were using ketotifen. CONCLUSION: Montelukast was used as add-on therapy with the inhaled corticosteroids to reduce the required dose of inhaled corticosteroids also the use of Montelukast lead to reduced number of exacerbations which will be reflected on the use of inhaled salbutamol and systematic corticosteroids. Also, Montelukast was superior to xanthines and ketotifen as an add-on therapy.