Mitochondrial syndrome is a metabolic disease, caused by punctiform mutations or depletions in nuclear and mitochondrial DNA. These genetic lesions alter mitochondrial oxidative phosphorylation, what leads to reduction in energy produced for cell activity. Particular severity of symptoms can be observed in organs and tissues highly dependent on oxygen metabolism. Symptoms can be seen in central and peripheral nervous system, skeleton muscles, pancreas, endocrine glands, kidneys and gastrointestinal tract. Diagnostics is difficult and expensive. It is based mainly on genetical assays and respiratory chain investigations in bioptate of skeleton muscles. So far the treatment is based on decreasing symptoms intensity. Presently studies are being conducted on gene treatment of this disorder, which aim is to provide evidence for efficacy of using respiratory chain co-factors in the treatment of mitochondrial syndrome.