A prospective randomized study was designed to compare phonatory mechanisms in patients treated with frontolateral partial laryngectomy (FLPL) with or without glottic reconstruction with false vocal fold (FVF) mucosal flap. Objective voice assessment was based on computerized acoustic recordings and videolaryngostroboscopy performed before, 1 year after, and 2 years after surgery. Phonatory mechanisms were studied according to the surgical technique and correlated with acoustic recordings. The results showed that supraglottic structures participated in laryngeal closure and voice production in 80% of cases in which a standard FLPL was performed. The FVF mucosal flap was involved in both laryngeal closure and voice production in 54% of patients treated with glottic reconstruction. The type of laryngeal closure (glottic or supraglottic) statistically influenced the acoustic measurements. As glottic closure is more frequent in patients treated with glottic reconstruction, the authors recommend performing reconstruction of the glottis with an FVF mucosal flap when an FLPL is indicated.