Assessment instruments that are not responsive to change are unsuitable as outcome tools in cardiac rehabilitation because they underestimate the psychosocial benefits of program attendance. Nine questionnaires were assessed for responsiveness with the standardized response mean (SRM). Questionnaires were allocated into 3 batteries, and each battery was completed by cardiac rehabilitation and comparison participants at 2 time points (411 and 375 participants in total, respectively). There was a high degree of variability in the responsiveness of instrument subscales. The positive affect subscale of the Global Mood Scale (J. Denollet, 1993a) was the most responsive (SRM = 0.62). Further information on the comparative responsiveness of psychosocial scales is important to optimize instrument selection for outcome studies.