The prevalence of Chronic Obstructive Pulmonary Disease is growing, and people are living with this disease well into older age. Little is known about how people with Chronic Obstructive Pulmonary Disease adapt to aging, particularly the physical changes of aging. According to the Identity Process Theory, people are inclined to attribute age-related changes in physical functioning to a transitory state of health, but not their physical health or appearance. Attributing one's physical functioning to aging itself makes people believe that they are physically "old" and enhances negative affect. We tested the Identity Process Theory using secondary physical functioning and physical health data collected from 87 pulmonary rehabilitation program participants with Chronic Obstructive Pulmonary Disease (age range = 47-82 years of age). Transient health states were participants' 6-Minute Walk Distance and perceived breathlessness during a time-limited exercise test using the Borg Rating of Perceived Exertion Scale. Participants' age-related changes in physical functioning were attributed to walk distances and their physical health to the physical changes of aging (X 2 = 18.55, df = 10, p = 0.05; GFI = 0.95; RMSEA = 0.10). These attribution patterns were replicated in the Borg Rating of Perceived Exertion model (X 2 = 13.34, df = 10, p = 0.21; GFI = 0.96; RMSEA = 0.06). The attributing of age-related changes in physical functioning to either transient health state circumvented their propensity for negative affect. Our findings are discussed in relation to maintaining physical functioning and general physical health promotion among Pulmonary Rehabilitation Program participants with Chronic Obstructive Pulmonary Disease.