Within this work, the application of the criterion based on correlation coefficient for comparative assessment of speech quality in speech rehabilitation for patients after surgical treatment of speech-producing tract oncological diseases is considered. The sequence of the actions intended for receiving comparative assessment of the speech quality by comparison of the sound recordings made before and after operation is considered. As a material for the assessment, a set of syllables from Standard GOST 50840-95 Speech transmission over varies communication channels. Techniques for measurements of speech quality, intelligibility, and voice identification are used. Also, a set of syllables, compiled on the basis of the analysis of most prone to postoperative change phonemes, is used. The previously proposed criteria based on the comparison of the intensity of time-normalized syllable records spectra have a fundamental drawback. They need an additional normalization of signal power. The proposed approach, based on the use of the linear correlation coefficient as a measure of similarity, does not have this drawback. The comparability of the values received using new criterion with the values received using previous version of the criteria is shown. Results of comparison confirm the possibility of the new criterion practical use.