In this prospective cohort study, we assessed voice outcome in patients before and up to 2 years after treatment for early glottic cancer either by radiotherapy or by laser surgery; 106 male patients, treated for T1aN0M0 glottic cancer either by endoscopic laser surgery (n = 67) or by radiotherapy (n = 39), participated in the study. Patients' voices were recorded and analysed pre-treatment and 3, 6, 12 and 24 months post-treatment at their routine visit at the outpatient clinic. Average fundamental frequency (F0), percent jitter, percent shimmer and normalized noise energy (NNE) were determined. After 2 years, local control rate was 95% in the radiotherapy group and 97% in the laser surgery group. Larynx preservation rate was 95% after radiotherapy and 100% after laser surgery. Voice outcome recovers more quickly in patients treated with laser surgery in comparison to radiotherapy: 3 months after laser surgery there is no longer a difference with regard to normal voices except for the fundamental frequency, which remains higher pitched, even in the longer term. For patients treated with radiotherapy it takes longer for jitter, shimmer and NNE to become normal, where jitter remains significantly different from normal voices even after 2 years. According to these results, we believe that laser surgery is the first treatment of choice in the treatment of selected cases of T1a glottic carcinomas with good functional and oncological results. © The Author(s) 2012.