Asthma may occur at any age and is the most common chronic disease of children. Numerous studies have shown a steady increase in the prevalence and incidence of asthma, and a similar trend is expected in the future. Asthma is a multifactorial caused disease. It is a chronic inflammatory disease of the bronchi characterized by reversible attacks of wheezing. In children with poorly controlled asthma, comorbidities are often present, especially GERD. Gastroesophageal reflux (GER) is the involuntary return of gastric content into the esophagus. GERD in developed countries has reached almost epidemic proportions, while in the poor countries is present in a smaller extent. If aggressive factors during GER overcome the defense mechanisms of protection and cause damage to the lining of the esophagus and/or cause symptoms of the disease, it is called gastroezophageus reflux disease (GERD) and it must be treated. Multi-channel intraluminal impedance (MII) of the esophagus is a newer method that is useful to confirm reflux disease, especially in cases of patients with refractory symptoms, to confirm the adequacy of antisecretory therapy, and to determine the presence of alkaline reflux . Numerous clinical trials confirm that the treatment of reflux disease improves symptoms of asthma and also to minimizes and reduces the need for medications. The examination, in often asymptomatic GERD in children with poorly controlled asthma, and even with other respiratory diseases, is essential because of their obvious connection. Diploma thesis describes the importance of the impedance of the esophagus as a new method in the diagnosis of GERD in children with poorly controlled asthma, and connection between GERD and asthma, using the available literature from scientific articles.