Until now few studies investigated the attentional demand of post-lexical processes in utterance production, showing controversial results and proposing few hypotheses about which attentional component may be used to encode motor speech. This thesis aimed to study if post-lexical processes recruit attention and to explore if attention is used as a global resource or if executive functions are specifically related to the planning of the utterance form. A series of dual-task paradigms was used with healthy young adults and two populations presenting a decreased performance in post-lexical processes: healthy older adults and participants presenting hypokinetic dysarthria due to Parkinson’s disease. Results suggest that attention is recruited for post-lexical processes as a global resource and that the shifting executive ability may also play a role in motor speech encoding. Finally, the magnitude of the dual-task interference between speech and non-verbal tasks is flexible with a potential role of task difficulty.