Background: Extra intestinal manifestations of inflammatory bowel disease (IBD) are a systemic illness that may affect up to half of all patients. Among the extra intestinal manifestations of IBD, those involving respiratory system are relatively rare. However, there is a wide variation of such manifestations, spanning from airway disease to lung parenchymal disease, pleural disease, enteric pulmonary fistulas and pulmonary function test abnormalities. This study aimed to detect the abnormalities of pulmonary function tests in inflammatory bowel diseases in children Method: A prospective Cross sectional study was carried out at Gastro entrology unit and pulmonary unit pediatric department, in Zagazig University hospitals during the period from December 2016 to January 2018. Twenty patients with inflammatory bowel disease were recruited in the study and full history and clinical examination was taken .full lab was drawan such as CBC,ESR ,CRP,LFT and KFT. pulmonary function tests (PFTs) was performed with spirometer. Statistical analysis was done for these data. Results: PFT was abnormal in 40% patients. abnormal PFT was classifed into restrictive 6 (30%), and obstructive defects 2 (10%) .IBD patients with active disease have abnormal pulmonary function tests .No relation of PFT abnormalities was found with age, sex, duration of disease, serum albumin, and hemoglobin levels, and other extraintestinal manifestation (arthritis/arthralgia) and drugs used to treat IBD. Conclusion: the study proved that IBD patients with active disease have abnormal pulmonary functions with predominant involvement of restrictive. Active IBD was more often associated with abnormal PFT than the disease in remission.