Single-ion attack by chlorides and multi-ion attack by chlorides and sulphates were compared with respect to the full probabilistic service life prediction of concrete structures, according to fib Bulletin 34. Especially the influence of sulphates on the chloride diffusion coefficient was investigated more thoroughly. Four concrete mixtures were tested, two Portland cement concretes and two blast-furnace slag concretes. Migration tests and natural diffusion tests were executed, based on NT build 492 and NT Build 443, respectively. Consequently, chloride migration and chloride diffusion coefficients were calculated. Based on the experimental results, the difference between both diffusion coefficients, measured after single-ion attack of chlorides as well as after multi-ion attack of chlorides and sulphates, is obtained. Finally, an input parameter was added to the service life prediction model taking into account the effect of the sulphate content. Additionally, the ageing factor and the transfer parameter were modified.