The purpose of this study was to determine the effectiveness of CPAP (Continuous Positive Airway Pressure) therapy on the treatment of hypernasality in patients with cleft lips and palates. 7 preschool children with severe hypernasality participated in the study. Acoustic measurements of nasality were done by using the NasalView (version 1.31). Results showed that the nasalance values were reduced linearly in both vowels according to the treatment period. The sharp treatment effect was observed at the beginning stage. The nasality values of the vowel /i/ showed a sharp decrease at the Evaluation Phase 1 and 2 and a small increase at the Phase 4 followed by a drop in the end. Further studies would be desirable for various patients with different disorder types.