PURPOSE: To verify the influence of word extension and the position of speech disruption within the syllable structure in the speech of stuttering and fluent adolescents and adults. METHODS: Participants were 120 individuals of both genders, with ages between 12 and 49 years and 11 months, who were divided into four groups: Research Group 1 (RG1) - 30 adolescents who stutter; Research Group 2 (RG2) - 30 adults who stutter; Control Group 1 (CG1) - 30 adolescents who do not stutter; Control Group 2 (CG2) - 30 adults who do not stutter. Speech samples containing 200 fluent syllables were gathered. Stuttered words were analyzed according to their extension (monosyllables, two, three or more syllables) and to the position of the disruption within the syllable (onset, nucleus or coda). RESULTS: Speech disruptions did not prevail in any of the possible types of word extension for the stuttering groups. However, for the groups of fluent individuals, speech disruptions were more frequent on monosyllabic words. As for the analyses of speech disruptions within the syllable, stutterers presented speech disruptions mainly on the onset position, whereas fluent individuals presented speech disruptions mainly on the nucleus of the syllable. CONCLUSION: Overall, results suggest that speech disruptions occur at the beginning of words and syllables, thus indicating difficulty in synchronizing phonological selection and activation. This fact happens independently of word extension.