Introduction: Malnutrition and cachexia are common in children with leukemia and are indicators of a bad prognosis. A poor nutritive state of a child is linked with an increased number of side-effects of treatment with poor response to treatment and a shorter period of survival. The functional state of children and the quality of their lives are worse. Purpose: The purpose of the thesis is to describe the problem of eating and drinking in children with leukemia. Methods: In the thesis, the descriptive work method with a critical review of domestic and foreign literature about the problem of eating and drinking of children with leukemia has been used. Discussion and completion: The nutritional treatment of children is a part of treatment in the case of leukemia. We have to start with it as early as possible. We start the nutritive support as soon after the diagnosis, regardless if the malnutrition is already present or if it is being assumed that the food intake will be decreased for more than 7-10 days. We need to compensate the difference between the actual food intake and the needs. The recommended way of nutritive support is the input of nutrients through the gastrointestinal tract (oral nutritional supplements, enteral nutrition). In the case that this is not possible, we introduce nutrients with parenteral nutrition. The energy needs in children with cancer are comparable with energy needs of children without cancer.