Children with pharmacoresistant epilepsy should be offered ketogenic dietary therapy. The diet, which is rich in fat and low in carbohydrate, has a beneficial effect in reducing seizures in this patient group. It may also have a beneficial effect in adults, but there is less evidence than in children. Dietary treatment of epilepsy is a specialist therapy, and in order to adhere to the diet, strong motivation of the patient and relatives as well as close follow-up from the specialist health service are necessary.