Introduction: Spasmodic dysphonia (SD) and muscle tension dysphonia (MTD ) are two different disorders with different etiology that influence the quality of voice, characterized by similar perceptual and acoustic features. It is known that the emergence of compensatory mechanisms can lead to problems in the differential diagnosis of adductor spasmodic dysphonia (ADSD) and primary hyperkinetic dysphonia (MTD) by fiberoptic video laryngoscopy (FLS). So, the goal of this paper is to determine acoustic objective differential diagnostic criteria for distinguishing between SD and MTD and confirm clinical laryngeal findings by FLS and diagnosis. Patients and methods: Eight women with MTD and eight women with SD diagnosed at the Department of Audiology and Phoniatrics of the Clinical Hospital Center Rijeka participated in this study. A phoniatrician and a speech language pathologist (SLP) participated in the diagnostic procedure. FLS and SLP assessment were performed. Samples of extended phonation of the vowel /a/ and reading were collected. The samples were analyzed in the computer program Praat, which was used to measure the duration of words and sentences, the percentage of brakes in phonation and words, and cepstral peak prominence (CPPS). Results: This study found that four acoustic parameters (word duration, sentence duration, percentage of brakes /a/, percentage of brakes (word)) separate SD and MTD well. CPPS does not separate these two groups of patients. Furthermore, it was confirmed that by analyzing the phonation pattern of the vowel /a/ in the computer program Praat it is possible to classify these two disorders with a cut-off value of 5%. If the percentage of delay in the phonation pattern of the vowel /a/ is greater than or equal to 5%, it is very likely that it is a voice sample of a person with SD. Conclusion: Acoustic measures applicable in clinical conditions were determined. It has been shown that acoustic analysis of voice samples can provide valuable differential diagnostic data. This suggests that acoustic analysis of voice samples should be an integral part of the standard diagnostic protocol for voice disorders besides FLS.