BACKGROUND: In recent years, there has been marked a tendency to a sharp increase in the number of children with complaints of pectus carinatum. The literature describes only a few cases report of a combination of keeled chest deformity with a more serious pathology of the spine - Scheuermann-Mau disease.AIMS: The aim of the work is to study the frequency, clinical manifestations and methods of timely diagnosis of combined structural lesions of the thoracic spine in children with keeled chest deformity.MATERIALS AND METHODS: The observational single-center cross-sectional study included patients from 5 to 176 years old with pectus carinatum. Categorical values ​​were described by indicating absolute values ​​and percentages in the sample, quantitative indicators corresponding to the criteria of normal distribution were described by using arithmetic means (M) and standard deviations (SD), boundaries of the 95% confidence interval; quantitative indicators not meeting the criteria for a normal distribution were descrided by using the median and interquartile range (Me, Q1Q3).RESULTS: Scheuermann-Mau disease was detected in 11 (9.3%) of 118 children with pectus carinatum. Pterygoid scapulae noted in 97 (82.2%) children with pectus carinatum, increased cervical lordosis in 93 (79.7%) children, and sloping, anteriorly adducted shoulders in 99 (83.9%) children significantly hampered the clinical assessment of the magnitude of thoracic kyphosis. Rigid thoracic kyphosis at the time of examination was formed in 1 16-year-old boy. In children of the younger age group (514 years old), Scheuermann-Mau disease had no clinical manifestations and was detected only during screening X-ray examination, while in the older age group (1516 years old), 3 out of 4 adolescents complained on the back pain. CONCLUSIONS: The frequency of occurrence of Scheuermann-Mau disease in children with pectus carinatum exceeds the average prevalence in the population. In patients with keeled chest pterygoid scapulae, excess cervical lordosis, and rounded shoulders sloping shoulders are associated with the difficulty of assessment the magnitude of thoracic kyphosis. Asymptomatic progression of Scheuermann-Mau disease is typical for younger children with pectus carinatum, and the complaints of pain syndrome and clinical picture of the disease develop only by the age of 15-16.Thus, all patients with pectus carinatum and posture disturbance should undergo a screening X-ray examination of the thoracic and lumbar spine in order to detect Scheuermann-Mau disease and start treatment in time.