In the era of immunochemotherapy, data on the long-term prognosis of elderly patients diagnosed with a diffuse large B-cell lymphoma (DLBCL) are scarce. In this population and on the longer term, other-cause mortality is an important competing risk that needs to be accounted for. Using clinical trial data and relative survival approaches, we estimated the 10-year net survival (NS) and we described the excess mortality hazard (EMH) due (directly or indirectly) to the DLBCL, over time and according to main prognosis factors using flexible regression modelling. The 10-year NS was 65% [59; 71]. Using the flexible modelling, we showed that the EMH decreases steeply after diagnosis. The variables 'performance status', 'number of extra-nodal sites' and the serum 'lactate dehydrogenase' were strongly associated with the EMH, even after adjustment on other important variables. EMH is very close to zero at 10 years for the whole population, so DLBCL patients do not experience an increased mortality compared to the general population in the long term. The number of extra-nodal sites was an important prognostic factor shortly after diagnosis, suggesting that it is correlated with an important but unmeasured prognostic factor that would lead to this selection effect over time.