Background Obstructive sleep apnea (OSA) and asthma are common inflammatory respiratory diseases of childhood. The similarities between and the parallel rise of both diseases raise the question of whether OSA is indeed more common in asthmatic children. Objectives The present study is cross section study conducted on fifty children with bronchial asthma the aim of study was to evaluate the frequency of obstructive sleep apnea in asthmatic patients, and impact of OSA on asthma control. Patients and Methods The present work is a Cross-sectional study conducted on fifty Children (27 females and 23 males) aging 5 to 18 years diagnosed as bronchial asthma following up in pulmonology clinic or admitted to pulmonology department in Pediatric Hospital- Ain Shams University. Patients were excluded from presence of any other chronic chest diseases, any congenital malformation in upper respiratory, any genetic disease or inborn error of metabolism, morbid obesity and other medical co morbidities that might interfere with sleep quality. All patients were subjected to full history taking, meticulous general and local chest examination, pulmonary function tests and exposed questionnaire: Asthma control questionnaire (ACQ) and OSA-18 quality of life questionnaire. Children were positive OSA with OSA-18 quality of life questionnaire referred to sleep study. Results 54 % of cases were females and 46% were males. There mean age=10.1, mean of OSA score =75.6. 20% diagnosed OSA according to questionnaire. OSA score increased in patients with history of PICU and hospital admission. OSA score was highly correlated with severity and degree of control of bronchial asthma. 10% of children were positive OSA with OSA-18 quality of life questionnaire suggestive have obstructive sleep apnea according to polysomnogram. Conclusion OSA has a direct and significant impact on asthma severity and control. Asthma and OSA are common disorders, and the concomitant presence of both conditions can be detrimental. Due to the bidirectional association of both conditions, we as clinicians should be aware of it.