ackground: Children and adolescents with diabetes mellitus mostly suffer from autoimmune mediated type 1 diabetes; however, in this age group rare forms of diabetes should also be taken into consideration. The correct diagnosis is crucial to initiate the appropriate treatment. Aim of the work and methods: Rare forms of diabetes in children are illustrated based on case examples and the corresponding clinical pictures are described in detail. After reading the article, the reader can better classify if a rare form of diabetes should be considered and appropriate diagnostics need to be initiated. Conclusion: In certain age groups, in the presence of clinical phenotypes, familial constellations and in cases of additional diseases/symptoms, rare forms of diabetes should be considered. In particular, a negative finding for autoantibodies associated with type 1 diabetes should sensitize to the presence of a rare form of diabetes. Correct diagnosis at an early stage is inherently important for the treatment of the respective patient.