We present experience of ketogenic diet (KD) applying in the treatment of pharmacoresistant epilepsy in a patients with glucose transporter deficiency syndrome type I (GLUT1). We observed six children with refractory epilepsy due to GLUT1. The high effectiveness of KD in the treatment of GLUT1 was demonstrated. All patients were achieved complete absence of seizures and EEG abnormalities from the beginning of KD. We noticed positive shift in cognitive and speech development for all children. Antiepileptic drugs were stopped taking due to the stable remission. There was a further positive dynamics in intelligence, psycho-emotional sphere; the children began to go a nursery school and a special school. Thus, the ketogenic diet is high effectiveness and, perhaps, the only method for GLUT1 treatment.