Abstract Background: Periodontitis is an inflammatory periodontal disease that is caused by bacterial plaque and destroys the connective tissue and bone that support the teeth. Patients with chronic kidney disease have damaged immunological systems because of uremic toxins and are thus prone to infections. Peritoneal dialysis (PD) is better for the removal of middle molecules (uremic toxins) than haemodialysis (HD). Our hypothesis was that PD is associated with a lower periodontal inflamed surface area (PISA). Methods: A cross-sectional study was performed on 58 consecutive patients on HD and 31 consecutive patients on PD. PISA was calculated using measurements of the clinical attachment level, recession and bleeding on probing. Results: Patients on PD had a 691 mm 2 (89%) lower PISA than patients on HD after adjustment for 15 possible confounders, including the duration of dialysis. The type of dialysis was independently correlated with PISA (semipartial correlation: -0.30; p=0.009; false discovery rate<5%). Conclusions: PD is associated with a smaller PISA independently of a large number of sociodemographic, lifestyle, laboratory and clinical factors.