Background. Acute otitis media in children is one of the most common causes of patients reporting to the family doctor and pediatrician. in rare cases, the inflammatory process spreads deeper into the temporal bone despite proper treatment, resulting in mastoiditis. Objectives. the aim of this article is to present the most common complication of inflammation of the middle ear. this is mastoiditis. the authors describe mastoiditis by means of its characteristics, the most common symptoms, incidence and treatment. Material and methods. data about the patients hospitalized in the Pediatric otolaryngology department of the Poznan university of Medical sciences from January 2017 to April 2018 was analyzed and subjected to a retrospective study. statistical analysis of the results was performed. Results. Based on the analyzed medical documentation, the incidence of mastoiditis was evaluated. in addition, the parameters characterizing the diagnostic procedure, along with the treatment methods and the effectiveness of the applied therapies in the hospital conditions, were assessed. the number of outpatient ambulatory visits and the frequency of necessary hospitalizations for patients with uncomplicated otitis media were additionally subjected to evaluation. Conclusions. the number of cases of inflammation of the middle ear requiring hospitalization in the Pediatric otolaryngology department Poznan university of Medical sciences is minimal, although the complications may present severe health consequences. uncomplicated acute otitis media may be successfully treated in ambulatory conditions by family physicians and pediatricians. early detection of the potential complication is essential in the practice of the family doctor. Summary ISSN 1734-3402, eISSN 2449-8580this is an open Access article distributed under the terms of the creative commons Attribution-noncommercial-shareAlike 4.0 international (cc By-nc-sA 4.0). license (http://creativecommons.org/licenses/by-nc-sa/4.0/).