A cadaveric study was performed to test the hypothesis that intact-canal-wall mastoidectomy (ICWM) with otoendoscopy allows for equal or better visualization of the middle ear cavity structures when compared with canal-wall-down mastoidectomy (CWDM) with microscopy. Ten temporal bones were prepared with a reversible canal-wall-down tympanomastoidectomy technique. Five anatomic sites in each middle ear cavity (lateral epitympanum, posterior crus of the stapes, the sinus tympani, eustachian tube orifice, and round window niche) were marked with paint. Two otolaryngologists blinded to the purpose of the study viewed the temporal bones with the microscope. Following replacement of the posterior canal walls, the bones were then viewed with a 30° and a 70° otoendoscope. All visualized paint marks for each viewing were recorded and compared. We found that ICWM with 30° or 70° otoendoscopy provided significantly better visualization of the sinus tympani than did CWDM (p ≤ 0.001). There was no significant difference among the three methods in visualization of the lateral epitympanum, posterior crus of the stapes, and round window niche. With respect to the eustachian tube orifice, one of the observers reported significantly better visualization with CWDM (p = 0.036). With adjunctive otoendoscopy, it is not necessary to remove the posterior canal wall to adequately visualize or remove disease from various areas of the middle ear cleft. The use of otoendoscopy during cholesteatoma surgery may allow for more frequent preservation of the posterior canal wall and reduced rates of residual cholesteatoma, given the equal or better visualization of the middle ear cavity.