Background: To evaluate the importance of larynx compartments in the prognosis of T3-T4a laryngeal cancer treated with transoral laser microsurgery. Methods: Two hundred and two consecutive pT3-T4a larynx carcinomas. Pre-epiglottic space involvement, anterior and posterior paraglottic space (PGS) involvement, vocal cord, and arytenoid mobility were determined. Local control with laser (LC), overall survival (OS), disease-specific survival (DSS), and laryngectomy-free survival (LFS) were evaluated. Results: The lowest LC was found in tumors with fixed arytenoid. In the multivariate analysis, positive margins (hazard ratio [HR] = 0.289 [0.085-0.979]) and anterior (HR = 0.278 [0.128-0.605]) and posterior (HR = 0.269 [0.115-0.630]) PGS invasion were independent factors of a reduced LC. Anterior (HR = 3.613 [1 .537-8.495]) and posterior ) PGS involvement were