This study assessed different cone beam CT (CBCT) imaging protocols for image-guided radiotherapy in prostate cancer patients. 844 CBCT images from 20 patients undergoing radiotherapy were analyzed. Daily online CBCT verification provided the best target coverage and lowest rectal dose compared to weekly online or offline protocols. Daily imaging helped improve target coverage, with one patient having inadequate coverage for 6 fractions with a weekly protocol versus just 1 fraction with daily imaging. The study concludes that daily online CBCT verification improves target coverage and reduces rectal dose for prostate cancer IGRT.