Background. Polypoid cystitis may simulate urothelial neoplasias cystoscopically and histologically. The frequency of polypoid cystitis is 0.38%; that among patients undergoing bladder catheterization is 6 %. Subjects and methods. The authors estimated the frequency of polypoid cystitis among chronic cystitis patients admitted to City Clinical Hospital Fifty, a base of the Clinic of Urology, Moscow State University of Medicine and Dentistry, in the period from February 2008 to February 2010. Out of 819 patients followed up, 3 who had diagnosed as having polypoid cystitis complained of pollakiuria, imperative micturate urges, and macrohematuria. They underwent ultrasonography, computed tomography, and cystoscopy; bladder masses measured 1.0, 7.0, and 11.5 cm, respectively; extensive growth was verified in 2 cases. Endoscopic studies identified procumbent rough-villous masses without well-defined outlines with the signs of bullous edema, decay, hemorrhages, and urinary salt encrustations. By taking into account the clinical picture and laboratory and instrumental findings, the authors suspected stage T3bNxMx bladder tumor in 2 patients and T1NxMx stage in 1. According to the European Association of Urology guidelines for management of bladder cancer, the patients underwent transurethral bladder resection. The patients were diagnosed as having polypoid cystitis on the basis of postmortem evidence. Results. In this study the frequency of polypoid cystitis was 37 %. Polypoid cystitis, a benign mass without a risk for malignancy, had signs of invasive transitional cell carcinoma. Conclusion. Such cases that rarely occur in practice are of clinical value and interest to urologists, pathologists, and oncologists.