Rationale: Obstructive sleep apnea and asthma often coexist; besides, they share a bidirectional influence towards the other condition. In adults, obstructive sleep apnea is more prevalent in men and asthma in women. However, during childhood, obstructive sleep apnea prevalence is equal in boys and girls while asthma has a strong influence of puberty in its prevalence, with pubescent girls more affected than boys. Objectives: To analyze the prevalence of obstructive sleep apnea in: 1) boys and girls and 2) severe asthma versus moderate and mild cases. We hypothesized that girls and severe asthma would have a higher prevalence of obstructive sleep apnea. Methods: Cross-sectional evaluation of asthmatic children attending a tertiary Pediatric Pulmonology clinic. Measurements: History, physical examination, Pulmonary Function Test, and Home Sleep Apnea Test. Main Results: We studied 80 consecutive patients, 7 to 18 years-old, mean age 11.6 years (standard deviation 2.7), 51.3% female, and 18.5% obese. Pulmonary Function Tests were obtained from 71 volunteers, 45% with obstruction pattern. Home Sleep Apnea Tests were available from 76 volunteers, with mean obstructive respiratory index of 1.8 events/h. Obstructive sleep apnea was found in 69 volunteers (86.2%). We did not find associations of obstructive sleep apnea and sex or asthma severity. Conclusions: Obstructive sleep apnea was frequent among these asthmatic children. Sex and asthma severity were not risk factors. Considering the interrelationship of both diseases, it is worth to keep in mind the possibility of obstructive sleep apnea among children and teenagers with asthma.