Purpose: The primary purpose of this study was to assess the effect of Lee Silverman Voice Treatment (LSVT®LOUD) on selected spectral/cepstral measures of voice in connected speech. Spectral/cepstral analyses also were used to descriptively compare changes in connected speech to those previously reported in sustained vowels. An additional goal was to examine individual differences in responses to LSVT across the spectral/cepstral measures. Methods: Nine adult participants with PD were examined in a pre/post treatment design. Speech recordings were obtained on three different days within one week before and one week after LSVT. Speech recordings were analyzed for cepstral peak prominence (CPP), CPP Standard Deviation (CPP-SD), Low/High Spectral Ratio (L/H SR), and Cepstral/Spectral Index of Dysphonia (CSID) using the Analysis of Dysphonia in Speech and Voice (ADSV) program. Results: CPP and CSID were the only measures that detect treatment-related changes in connected speech. Investigating individual differences demonstrated more participants exhibiting an improvement in sustained phonation than in connected speech. Conclusions: Cepstral/spectral measures have been shown to be valid measures for estimating dysphonia severity in both continuous speech and sustained vowels. In addition, it extends the use of the cepstral/spectral measures for characterizing speech and voice aspects prior to treatment and for quantifying treatment outcomes. Moreover, it supports the use of LSVT as a treatment approach for improving voice quality in addition to intensity in PD.