In addition to a neutron source as a treatment device, to conduct boron neutron capture therapy (BNCT), several peripheral devices are needed such as a treatment planning system, patient positioning system, and neutron dosimeters. In particular, the treatment planning system is an indispensable tool for BNCT, as well as for other radiation therapy modalities. Before the treatment, the treatment planning system is used to find optimal irradiation conditions for the patient with the help of irradiation simulations. Radiation dose calculations in BNCT treatment planning utilize mainly the Monte Carlo transport method due to the complexity of neutron interactions within the patient. For reactor-based BNCT, several treatment planning systems were developed and applied to actual BNCT clinical trials. Currently, new commercial treatment planning systems applicable to accelerator-based BNCT are under development. Many fundamental techniques included in the treatment planning systems for the reactor-based BNCT are applied in the new systems. This chapter introduces the basics of BNCT treatment planning, including BNCT dose components and applied dose calculation methods, and several treatment planning systems developed worldwide.