Background: PMRI is a standard pre-RT evaluation procedure in pts with intermediate and high-risk prostate cancer. We conducted a retrospective study to evaluate an influence of PMRI to delineation of RT clinical target volume (CTV). Methods: Medical records of prostate cancer pts treated with intensity-modulated RT (IMRT) in single institution retrieved and examined retrospectively. Initial risk group affiliation was defined using D'Amico method. PMRI reports of pts with intermediate and high-risk prostate cancer were reviewed and risk group affiliation was re-defined in regards of T- and N-stage. IMRT treatment plans were re-assessed. In regards to PMRI T-stage, extra-capsular extension (ECE) and seminal vesicles invasion (SVI) were included to high-dose CTV. Pelvic lymph nodes (PLN) were planned to treat in all high-risk pts. PLN considered pathological by PMRI were included to separate CTV to receive RT dose higher than unaffected PLN stations. Results: Between 2008 and 2014, 169 pts with intermediate and high-risk prostate cancer underwent PMRI at around 1 month before commencing IMRT. Initially, 89 pts were affiliated to intermediate-risk and 80 to high-risk group. In general, PTV-changes based on PMRI data required in 77 pts (45.5%). Thirty seven of 89 intermediate-risk pts (41.6%) have been switched to high-risk group, necessitating irradiation of PLN. ECE and SVI were included to high-dose CTV in 64 (37.8%) and 29 pts (17.2%) respectively. PLN were thought pathological in 10 pts (5.9%), which demanded contouring of a separate CTV. Conclusions: In our series PMRI-scans had a significant impact on RT target coverage decision in pts with intermediate and high-risk prostate cancer.