In this study was to investigate the сoexistence of diabetes mellitus type 1 with other chronic pathology in children and adolescents and their impact on the course of diabetes mellitus type 1 (DM1). The 88 children from 3 to 17 years who had DM1 were observed. The study was conducted by survey with the aim of finding risk factors and associated comorbidties with a questionnaire-based, objective-subjective study. All patients had severe form of T1DM, with suboptimal and poor glycemic control. Comorbid pathologies observed in 71,6±4,8% of childrn included: thyroid pathology – 62,5±5,1%, disorders of the autonomic nervous system – 20,5±4,3%, gastro-pathology – 7,9±2,8%, atopic dermatitis – 6,8±2,6%, arthritis – 6,8±2,6%, bronchial asthma – 4,5±2,2%, allergic rhinitis – 3,4±1,9%, immune-deficient disorder – 2,3±1,5%. Conclusions. 1. The detected comorbid pathology in children with DM1 makes it necessary to collect an anamnesis and examination of children for the purpose of early finding a coexistence of chronic pathology. 2. The risk of development of the thyroid pathology enhances is 7,5 times, allergic pathology is 6,9 times in patients with DM1. 3. Coexistence of type 1 diabetes and other chronic diseases impairs glucose metabolism, impedes effective insulin therapy, and deteriorates diabetes control. 4. This accent the need for the improvement of the monitoring of patient with diabetes mellitus and comorbid pathology for the prognosis of the course and optimization of treatment and rehabilitation measures.