Chronic kidney disease (CKD) is a growing public health problem. Individuals in all stages of CKD are at higher risk for development of cognitive impairment and this may be a major determinant in their quality of life (QOL). The prevalence of cognitive deficits is particularly high in subjects with end-stage renal disease (ESRD). While it is sufficiently well documented that ESRD is linked with a change in cognitive function, little is known about the influence of different dialysis modalities on cognitive function. The effect of dialysis modality on risk of cognitive impairment is unclear. Some data suggest that patients with ESRD treated with chronic ambulatory peritoneal dialysis (CAPD) had consistently better cognitive function than patients treated with haemodialysis (HD). We concluded that the previously observed apparent difference between two modalities of dialysis treatments resulted either from very low dialysis delivery or comparison with poorly matched controls. Regarding these data from previous studies we hypothesised that well-dialysed, well-nourished and medically stable HD patients had no cognitive dysfunction in comparison with well-dialysed, well-nourished, medically stable and demographically matched CAPD patients. Also, future studies are needed to differentiate between modality as a risk factor from the factors contributing to selection bias among patients choosing CAPD over HD.