Based on 8 observations, the authors analyze the extension of middle ear cholesteatomas on the anterior attic and the anterior supralabyrinthine cellular groove, the internal retrotympanum and the posterior sublabyrinthine cellular groove, the hypotympanum and the anterior sublabyrinthine groove, the retrolabyrinthine region and the translabyrinthine and posterior supralabyrinthine grooves. Despite progress in imaging and optical instrumentation, exact precision of the lesions sometimes remains impossible. The patient must be warned of a possible enlargement of the operative pathway and its consequences.