BACKGROUND New-onset diabetes after transplantation (NODAT) is a serious complication after a solid organ transplant. NODAT occurs in 2% to 53% of all solid organ transplant recipients. The identification of high-risk patients and the implementation of measures to limit the development of NODAT can improve the long-term patient prognosis. MATERIAL AND METHODS Our study group consisted of 336 patients undergoing heart transplant. Patients with prior diabetes (60 patients) were excluded from analysis. The remaining 276 patients were divided in 2 groups: with NODAT (n=109) and without NODAT (n=167). Logistic regression analysis was used for NODAT risk factor assessment. RESULTS NODAT occurred in 109 (32%) out of 336 patients without diagnosed diabetes before heart transplantation. Risk factors for post-transplant diabetes mellitus, which was shown by the analysis of the collected data, were BMI at discharge (OR=1.082, CI 1.011-1.158, p=0.0233), history of diagnosed CMV infection (OR=1.464, CI 1.068-2.007, p=0.0179), and age over 51 years (OR=1.634, CI 1.274-2.095, p=0.0001). CONCLUSIONS 1. New-onset diabetes after transplantation (NODAT) or long-lasting hypoglycemia (over 2 years after transplantation) was diagnosed in 32% patients after heart transplantation developed. 2. The risk factors of NODAT were BMI at discharge and history of diagnosed CMV infection, and age over 51 years was an independent risk factor.