BACKGROUND Radiotherapy is explicitly indicated as one of the excluding factors in diagnosing overactive bladder syndrome (OAB). Nevertheless, symptoms of OAB such as urgent episodes, incontinence, pollakiuria, and nocturia, which are consequences of irradiation, led us to test the effectiveness of VESIcare®/Solifenacin in patients demonstrating these symptoms after radiation therapy of small pelvis organs due to malignant neoplasm. MATERIAL AND METHODS We conducted an observatory clinical study including 300 consecutive patients with symptoms of post-irradiation bladder; 271 of those patients completed the study. The observation time was 6 months and consisted of 3 consecutive visits taking place at 12-week intervals. We used VESIcare® at a dose of 5 mg a day. Every sixth patient was examined urodynamically at the beginning and at the end of the observation period, with an inflow speed of 50 ml/s. RESULTS We noticed improvement and decline in the average number of episodes a day in the following parameters: number of micturitions a day (-36%, P<0.01), nocturia (-50%, P<0.01), urgent episodes (-41%, P<0.03), and episodes of incontinence (-43%, P<0.01). The patients' quality of life improved. The average maximal cystometric volume increased by 34 ml (21%, p<0.01), average bladder volume of "first desire" increased by 42 ml (49%, P<0.01), and average detrusor muscle pressure at maximal cystometric volume diminished by 9 cmH2O (-36%, P<0.03). CONCLUSIONS The substance is well-tolerated. Solifenacin administered long-term to patients with symptoms of OAB after radiotherapy of a malignant neoplasm of the small pelvis organs has a daily impact in decreasing number of urgent episodes, incontinence, pollakiuria, and nocturia.