Abstract： Background Surgical treatments for chronic suppurative and cholesteatoma otitis media have been discussed for several decades, but recurrences still occur because of the complex dissection required and hidden lesions associated with otomastoiditis. This study investigated the technology and strategy behind the use of otoendoscopic-assisted otosurgery.Methods We reported on hidden lesions in 32 ears of patients with otomastoiditis between November 2006 and January 2009. All the patients were treated with the aid of an otoendoscope. The advantages of otoendoscopy, including multi-angle light scattering, aperture illumination, and magnification of the local operative field, were utilized in otologic microsurgery, and otoendoscopic operative techniques were introduced for operative sites such as the epitympanum, aditus of the antrum, facial recess, sinus tympani and the mastoid tip.Results All patients were followed up from 3 months to 2 years after surgery. All patients recovered well within 3 months following surgery, except for one case of epithelialization of the mastoid cavity occurring 6 months after surgery for cholesteatoma on the cerebellar surface and another case with Bezold's abscess, hyperplastic granulation tissue developed at the antrum.Conclusions Otoendoscopy can overcome the technical deficiency of rectilinearity of the visual axis associated with otomicroscopic illumination, which presents a problem when dealing with otomastoiditis lesions in hidden areas. This technique allows such lesions within the complex three-dimensional structure to be visualized and cleaned. Otoendoscopy thus has significant potential for improving the quality of surgery and reducing the risk of postoperative recurrence.