Background. Differences in the epidemiology of posttransplant lymphoproliferative disease (PTLD) between adult and paediatric kidney transplant recipients remain unclear. Methods. Using the Australian and New Zealand Dialysis and Transplant Registry (1963-2015), the cumulative incidences of PTLD in children (age <20 years) and adults were calculated using a competing risk of death model and compared with agematched population-based data using standardized incidence ratios (SIRs). Risk factors for PTLD were assessed using Cox proportional hazards regression. Results. Among 23 477 patients (92% adult, 60% male), 505 developed PTLD, with 50 (10%) occurring in childhood recipients. The 25-year cumulative incidence of PTLD was 3.3% [95% confidence interval (CI) 2.9-3.6] for adult recipients and 3.6% (95% CI 2.7-4.8) for childhood recipients. Childhood recipients had a 30-fold increased risk of lymphoma compared with the age-matched general population [SIR 29.5 (95% CI 21.9-38.8)], higher than adult recipients [SIR 8.4 (95% CI 7.7- 9.2)]. Epstein-Barr virus (EBV)-negative recipient serology [adjusted hazard ratio (aHR) 3.33 (95% CI 2.21-5.01), P<0.001], year of transplantation [aHR 0.93 for each year after the year 2000 (95% CI 0.88-0.99), P0.02], induction with an agent other than anti-CD25 monoclonal antibody [aHR 2.07 (95% CI 1.16-3.70), P0.01] and having diabetes [aHR 3.49 (95% CI 2.26-5.38), P<0.001] were independently associated with PTLD. Conclusions. Lymphoma occurs at similar rates in adult and paediatric recipients, but has been decreasing since the year 2000. EBV-negative patients and those with diabetes or induction agent other than anti-CD25 monoclonal antibody are at substantially increased risk of PTLD.