Osteoprotegerin (OPG), a natural decoy receptor for osteoclast differentiation factor, is produced by osteoblasts in response to PTH. OPG and its ligand RANKL constitute a complex mediator system involved in the regulation of bone resorption, probably playing an important role in the homeostasis of bone turnover. Osteoprotegerin has emerged as an independent predictive factor of atherosclerosis and vascular calcification in hemodialysis patients. Sparse data are available on the evolution of osteoprotegerin after renal transplantation. The aim of this study was to investigate the importance of OPG in pediatric dialysis patients and renal transplantation recipients. Twenty-six patients on chronic hemodialysis (HD) (14 males, 12 females, aged 15.1±2.2 years) and 18 patients on continuous ambulatory peritoneal dialysis (CAPD) (8 males, 10 females, aged 13.7±3.5 years), 20 renal transplantation recipients (11 males, 9 females aged 15.3±2.8 years), and 18 gender and age matched healthy children were included in the study. Laboratory investigation included complete blood count, biochemical tests in serum, C-reactive protein, fibrinogen, ceruloplasmin, albumin, prealbumin and intact parathormon levels (PTH). Serum OPG levels were measured by enzyme-linked immunosorbent assay. The mean OPG levels of dialysis patients were significantly higher than those of the renal tx group and the control group (p<0.05). The mean OPG levels were similar in HD and CAPD patients (p>0.05). Also, there was no significant difference between OPG levels of the renal tx group and the control group (p>0.05). There was significant correlation between OPG levels and calcium (Ca) and alkaline phosphatase levels in all patients. We couldn’t find any correlation between OPG levels and inflammation markers such as C-reactive protein, fibrinogen and ceruloplasmin levels in all groups. There was a negative correlation between OPG levels and age in the renal transplant recipients, but we did not observe any relation between OPG levels and sex, duration of transplantation, hypertension, dyslipidemia, immunsuppressive therapy, and glomerular filtration rate. This study demonstrates that kidney transplantation has improving effect on renal bone disease. However, these preliminary results should be confirmed with further studies.