New-onset diabetes mellitus after transplantation (NODAT) is defined as diabetes which developed after organ transplantation. NODAT occurs in approximately 16-20% of recipients one year after kidney transplantation and is the main factor for the increased mortality and morbidity, increased medical costs, progressive graft failure and decreased patients' quality of life. Determination of phenotypic risk factors allows to define the scale of the risk of NODAT and can be helpful in detecting patients at risk of post-transplant diabetes. Overweight and obesity are well-known phenotypic risk factors that can be modified by lifestyle-change intervention. Adequate education about the principles of healthy lifestyle is one of the most important prevention factors. The medical staff should organize health education which should begin long before the planned transplantation, even at the stage of predialysis treatment or dialysis and be continued after transplantation. Early assessment of the risk of developing glucose metabolism disorders also allows the selection of immunosuppressive therapy less likely to affect carbohydrate metabolism. The article presents examples of simple risk scores and also principles of prevention and treatment of NODAT. The article presents the definition of NODAT, risk factors, especially overweight or obesity, risk scores and also principles of prevention and treatment of NODAT.