Introduction. Paget’s disease of bone (osteitis deformans) is a rare metabolic disorder of bone remodeling with complex etiology. In the most cases, it is detected by coincidence, during nuclear medicine and radiological diagnostic procedures. Herein we report a case of advanced prostate cancer coexisting with asymptomatic Paget’s disease. Case report. We present a 69-year-old patient, with biochemical recurrence two years after radical prostatectomy for localized prostate cancer and period of stable remission. During the evaluation of metastatic spread of prostate cancer, the bone scintigraphy with technetium diphosphonate showed diffuse areas of increased radiotracer uptake in the left leg long bones and focal changes in the axial part of the skeleton. Scintigraphic findings led to a differential diagnostic dilemma regarding etiology of bone changes, so it was supplemented by standard radiologic methods and laboratory evaluation of bone metabolism parameters. The existence of asymptomatic polyostotic Paget’s disease and metastatic bone changes was found at the same time. Conclusion. Metastatic bone lesions, in this case from prostate cancer, and asymptomatic Paget’s disease may closely resemble each other. They both need careful evaluation in order to determine the proper stages of malignant disease and selection of appropriate therapies for patients.