Abstract Purpose - To evaluate what effect spreading the maintenance BCG regimen from 12 to 18 months has on the treatment completion rate. Patients and methods - Retrospective data about patients diagnosed with intermediate or high risk nonmuscle invasive bladder cancer were collected. Suggested regimen started with 6 weekly induction intravesical full dose BCG instillations followed by 3 weekly instillations, 3 months after the 6th instillation. Thereafter, 3 weekly instillations were delivered 6 months after the 9th and the 12th instillation. In total, 15 BCG instillations were administered within 18 months. Cystoscopy and urine cytology were performed one month following the 6th, 9th, 12th and 15th instillations and then according to guidelines Results - 195 patients met the inclusion criteria. 190 (97.4%) patients completed the induction instillations and 141 (72.3%) completed the treatment protocol. 39 patients discontinued treatment for medical reasons and 15 patients due to non-compliance. 162 patients completed follow up as recommended for a median of 46±20.1 months. Of those, 45 patients (27.8%) and 8 (4.9%) had disease recurrence and progression, respectively. Conclusion - Spreading BCG instillations during maintenance protocol might achieve a better treatment completion rate, mainly due to improved patient compliance. No impacts on recurrence and progression rates have been observed in our cohort. Prospective randomized trials are warranted before suggesting clinical application.