Accurate illness perceptions are essential to the self-management of chronic illness. This study explored trajectories of illness perceptions in persons with morbid obesity (n = 53) and persons with chronic obstructive pulmonary disease (n = 52) following a patient education course. Participants completed the Brief Illness Perception Questionnaire five times over a 1-year period. Repeated measures analysis of variance was employed. Over time, obese participants perceived shorter illness duration, fewer consequences, less emotional stress, and more personal control. Chronic obstructive pulmonary disease participants had initial increases in personal control and understanding, but these changes were not maintained throughout the follow-up period.