This prospective longitudinal observational study compared the ability of second-look surgery with that of surveillance using serial non-echo-planar diffusion-weighted imaging to detect residual cholesteatoma after canal wall-up mastoidectomy. A total of 34 patients were included in the study who underwent canal wall-up mastoidectomy and had an initial negative diffusion-weighted imaging scan 9-12 months after their initial surgery. Of the 34 patients, 13 patients had subsequent second-look surgery and 21 were monitored with serial diffusion-weighted imaging for at least three years. Of those patients who had second-look surgery 15% had residual disease, but 23% had postoperative complications, such as postoperative infections and hypertrophic scars. Of those 21 patients who had serial imaging, 14% were lost to follow-up after the first year. Of those remaining patients, 11% had imaging positive for cholesteatoma at their two-year scan whilst, at three years, 75% of patients had negative scans, with the other 25% being lost to follow-up. Whilst second-look surgery remains the gold standard to be able to check for residual or recurrent disease, this study raises an interesting point regarding the use of consecutive diffusion-weighted imaging for three years as a means of avoiding surgery and its potential complications. The authors do note the high rate of loss to follow-up at three years, which needs to be borne in mind when adopting diffusion-weighted imaging to check for postoperative cholesteatoma.