Mutations in the mitochondrial genome can cause mitochondrial diabetes. We present two cases in which the same mutation, mtDNA3243A>G, caused two different phenotypes: maternally inherited diabetes and deafness and mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes. Mitochondrial disease can imitate a variety of common con-ditions and should be considered in the case of multisystem disease, complex neurological symptoms or neurological symptoms combined with symptoms of other organ systems.