['To determine whether narrow band imaging (NBI) improves detection of non-muscle-invasive bladder cancer over white-light imaging (WLI) cystoscopy.', 'We conducted a prospective, within-patient comparison on 103 consecutive procedures on 95 patients scheduled for (re-) transurethral resection of a bladder tumor (84) or bladder biopsies (19) in the Academic Medical Center, Amsterdam (September 2007-July 2009) and in the General Faculty Hospital, Prague (January 2009-July 2009). WLI and NBI cystoscopy were subsequently performed by different surgeons who independently indicated all tumors and suspect areas on a bladder diagram. The lesions identified were resected/biopsied and sent for histopathological examination. Number of patients with additional tumors detected by WLI and NBI were calculated; mean number of urothelial carcinomas (UCs) per patient, detection rates, and false-positive rates of both techniques were compared.', 'A total of 78 patients had a confirmed UC; there were 226 tumors in total. In 28 (35.9%) of these patients, a total of 39 additional tumors (17.3%) (26pTa, 6pT1, 1pT2, 6pTis) were detected by NBI, whereas 4 additional tumors (1.8%) (1pTa, 1pT1, 2pTis) within 3 patients (2.9%) were detected by WLI. The mean (SD, range) number of UCs per patient identified by NBI was 2.1 (2.6, 0-15), vs 1.7 (2.3, 0-15) by WLI (P <.001). The detection rate of NBI was 94.7% vs 79.2% for WLI (P <.001). The false-positive rate of NBI and WLI was 31.6% and 24.5%, respectively (P <.001).'] Does narrow band imaging cystoscopy improve the detection of non-muscle-invasive bladder cancer?