This observational study compared global self-esteem and physical self scores and their stability over a three-week period in patients with chronic obstructive pulmonary disease (COPD) and healthy adults, through the analysis of day-today time series. Two groups were formed: a COPD group of 27 patients with stable and moderate COPD, and a control group of 31 " healthy " adults. The results showed lower mean scores over the study period for global self-esteem, physical self-worth, and each of the physical self subdomains in COPD patients as compared with the " healthy " group. Moreover, the results showed less stability in global self-esteem, physical self-worth, and the physical self subdomains over the same period in these patients. Our principal findings support the assertion of Kernis and colleagues that unstable global self-esteem and physical self reflects a certain vulnerability to endogenous and exogenous events.