Purpose: To examine the effects of cognitive-linguistic deficits and respiratory physiologic changes on respiratory support for speech in individuals with Parkinson's disease (PD) using two speech tasks: reading and extemporaneous speech. Method: Five women with PD, 9 men with PD, and 14 age- and sex-matched control participants read a passage and spoke extemporaneously on a topic of their choice at comfortable loudness. Sound pressure level, syllables per breath group, speech rate, and lung volume parameters were measured. Number of formulation errors, disfluencies, and filled pauses were counted. Results: Individuals with PD produced shorter utterances compared with control participants. The relationships between utterance length and lung volume initiation and inspiratory duration were weaker for individuals with PD than for control participants, particularly for the extemporaneous speech task. These results suggest less consistent planning for utterance length by individuals with PD in extemporaneous speech. Individuals with PD produced more formulation errors in both tasks and significantly fewer filled pauses in extemporaneous speech. Conclusion: Both respiratory physiologic and cognitive-linguistic issues affected speech production by individuals with PD. Overall, individuals with PD had difficulty planning or coordinating language formulation and respiratory support, particularly during extemporaneous speech.