The purpose of this study was to compare nasalance scores of the experimental vowels, words and paragraphs with and without ‘Hypernasality Control Device (HCD)’ in adults with hypernasality. Three adults with a cerebrovascular attack or a Parkinson’s disease wore in HCD, were asked to read aloud the experimental vowels, words and paragraphs. Using a Nasometer, the nasalance scores were measured. In all experimental vowels, words and paragraphs, the nasalance scores with HCD were measured lower than those without HCD. These results showed that HCD played a role in regulating nasal resonance in adults with hypernasality. However, various modifications and trials of HCD are required for the adequate modulation of nasal resonance. Additional studies are also required for adults with various degrees of hypernasality.