Bone metastases in prostate cancer constitute the most frequent cause of systemic failure in treatment, which results in numerous complications and finally leads to patient's death. Pain is one of the first and most important clinical symptoms of bone metastases and can be found among more than 80% of patients. Therefore, the most analgetic effective and simultaneously the least toxic treatment is an important point of therapeutic management in this group of patients. The aim of this prospective clinical trial was a comparison of analgetic effectiveness and toxicity of monotherapy with 153Sm isotope to combined therapy (153Sm + EBRT) among patients diagnosed with multiple painful bone metastases due to CRPC (mCRPC). 177 patients with mCRPC were included into the prospective randomised clinical trial in which 89 patients were assigned to the 153Sm isotope monotherapy, while 88 patients were assigned to the combined therapy including 153Sm isotope therapy and EBRT. All patients were diagnosed (bone scan and X-ray or/and CT or/and MRI) with painful bone metastases (bone pain intensity >= 6 according to VAS classification). The following additional inclusion criteria were established: histologically confirmed adenocarcinoma of prostate, multifocal bone metastases, no prior chemotherapy or palliative radiotherapy to bone. All patients signed informed consent.The combination of the isotope therapy with EBRT was more effective analgetic treatment than isotope therapy alone. The highest pain decline was noticed in the first weeks after treatment termination. In the whole group, a total or partial analgesic effect was observed among 154 (87%) patients while among 23 (13%) patients there was a lack of analgesic effect or even pain intensification. The results of this clinical trial demonstrated that for patients with multiple mCRPC it is recommended to combine the 153Sm isotope therapy with local EBRT because of a greater analgetic effect. It is important to note that combined therapy did not intensify the toxicity of treatment.