The aim of this study was to evaluate and compare the quality of life and glycaemic control in children with type 1 diabetes (T1D) and associated autoimmune diseases with T1D only, using the Pediatric Quality of Life Inventory Generic Core Scale. The study examined differences in health-related quality of life assessments and glycaemic control between children with T1D and associated autoimmune diseases and T1D only. In total, 94 children, aged 2 to 17 years, and their parents participated in the study. The results of the study showed a statistically significantly lower total score of general well-being for children with T1D and associated autoimmune disease (