<b>Introduction:</b> It has been stablished a correlation between asthma and obstructive sleep apnea-hypopnea syndrome (OSAHS), but there are not enough studies between the apnea-hypopnea index (AHI) and pulmonary function tests in the child population. The objective of this study, was to determine the correlation between the pulmonary function tests index and the apnea-hypopnea index in asthmatic children that attend the Fundación Neumológica Colombiana. <b>Methods:</b> An observational, retrospective study was conducted in children of 3-12 years with clinical diagnosis of asthma, and a polysomnography was performed. Were included patients that, besides having diagnosis of asthma and OSAHS, had spirometry or impulse oscillometry (IOS). Tests Spearman and U Mann Whitney were used to determine the correlation between the AHI and the pulmonary function tests index – forced expiratory volume in 1 second (FEV1), forced vital capacity (FVC), FEV1/CFV ratio, resistance (Rrs), respiratory system reactance (Xrs) to 5 and 20 Hz (Rrs5, Rrs20, Xrs5) pre and post-bronchodilator. Results: 64 patients, 59,4% masculine, mean age 6,72 years, mean body mass index (BMI) 17,55 kg/m2. 59,4% moderate-severe asthma, 59,4% non-control asthma. There was found a significant and inverse correlation within the variables FEV1, FEV1/FVC, R5 and the AHI. There was no significant correlation between severe OSAHS and moderate-severe or non-control asthma. <b>Conclusions:</b> There is a negative significant correlation between the AHI and the pulmonary function index FEV1, FEV1/FVC, R5, which suggests a correlation between the airway diameter and the severity of the OSAHS.