Participants representing four medical diagnoses commonly associated with communication disorders were recruited to evaluate the function of the CPIB across different disorder groups. The four groups were multiple sclerosis (MS), Parkinson’s disease (PD), amyotrophic lateral sclerosis (ALS), and head and neck cancer (HNCA; oral, oral-pharyngeal or laryngeal cancer, and including those treated with laryngectomy). These groups were chosen for several reasons. First, they are adult-onset conditions, and therefore participants have experienced living as ‘typical’ communicators before the onset of the condition. That provides a perspective of change from which participants can evaluate the impact of the health condition on communicative participation. Because the impact of health conditions on communicative participation has not been directly compared between groups with acquired versus congenital conditions, the decision was made in this study to focus on acquired conditions. Second, the communication disorders associated with these conditions are largely motor speech and voice disorders. In this study, the goal was to target groups who were more likely to retain relatively strong language and cognitive skills because the sole method of data collection was self-report without the presence of a researcher to assist participants with the questionnaires. Finally, these four groups represent different speech and voice disorder characteristics with different trajectories (e.g., stable, slowly degenerative, more rapidly degenerative). This diversity was desired to examine the function of the CPIB items in varying populations.