Abstract The effectiveness of transmutation for long-lived fission products (LLFP) in light water reactors (LWR), i.e. both BWR and PWR, considering the large capture cross-section of FPs in thermal region was evaluated. Calculation results of iodine and technetium transmutation in BWR and PWR suggested an effective use of BWR as compared to PWR. To obtain transmutation fraction [TF] of 30 to 40%, the irradiation period needed for 99Tc transmutation was estimated as 10 to 15 years, and the period for 129I transmutation was estimated as 30 to 40 years, respectively. The evaluations bring a new concept of multi-recycle LLFP transmutation using LWR TR (LWR for transmutation).