In the May issue of BJUI Miki N Hew et al. discuss differences in renal function evolution between patients with renal cell carcinoma (RCC) submitted to radical nephrectomy (RN) and living kidney donors matched for age and gender. They also assessed the role of co-morbidities like hypertension, diabetes and cardiovascular disease as a risk factor for developing an estimated glomerular filtration rate (eGFR) of <60mL/min/1.73m2. This is a retrospective study between January 2000 and February 2011. Renal function was compared between the groups using the Modification in Diet and Renal Disease (MDRD) equation at one year after RN. One hundred and ninety-six patients were included, 98 in each group. The one-year postoperative mean eGFR (available in 89 patients with RCC and 87 donors) was similar, at a mean (SD) of 56.7(16.4)mL/min/1.73m2 in patients with RCC and 56.2(9.8)mL/min/1.73m2 in donors (P=0.83). In patients with RCC the incidence and severity of co-morbidities was significantly higher. A preoperative eGFR of 60-89mL/min/1.73m2 was the only independent risk factor for developing a postoperative eGFR of <60mL/min/1.73m2 (odds ratio 4.4, confidence interval 2.1-9.5, P<0.001, 95% confidence interval). In the present study the only explanatory reason for this finding was the better preoperative renal function of the donor group (higher eGFRs). In conclusion, after RN, patients with RCC and living kidney donors matched for age and gender had similar renal function at six months and one year postoperatively, despite a higher co-morbidity load and lower baseline renal function in the patients with RCC.