End-stage renal failure requires replacement of kidney function by different methods, the best of them being renal transplantation owing to significant survival advantage and better quality of life compared to the other renal replacement therapy methods. This is a case-series study that was done at the Department of Nephrology, Arterial Hypertension, Dialysis and Renal Transplantation at University Hospital Centre Zagreb where we tried to demonstrate correlation between renal transplantation and influence of rare diseases on post-transplantation period. In this study, seven patients with rare diseases were included, all of them being transplanted and treated for primary disease. Rare diseases and their effects on kidney function that are discussed in this study are Primary hyperoxaluria type I, Fabry disease, Atypical haemolytic-uremic syndrome, Tuberous Sclerosis Complex, Turner syndrome and Dandy-Walker syndrome. Four percent of people on renal replacement therapy in Croatia have idiopathic chronic kidney disease, and high proportion is administered under the diagnosis of chronic glomerulonephritis, diabetic nephropathy and nephroangiosclerosis. It is probable that some of these patients have rare diseases that are not diagnosed and are responsible for graft failure in post-transplantation period due to untreated primary disease. Screening for rare diseases in pre-transplantation period would improve overall outcome of transplantation in these patients. This study emphasizes the importance of early diagnosis and treatment of rare disease and their effect on post-transplantation period.