Despite strong evidence supporting the benefits of physical activity in managing and preventing diabetes, the majority of Canadians living with or without diabetes are insufficiently active to achieve health benefits. The purpose of this study was to examine the difference in key physical activity-related, psychosocial constructs from major social-cognitive theories/models for individuals with type 1 diabetes (n = 695), type 2 diabetes (n = 1540) and those without diabetes (n = 829). The relatively similar scores reported for the social-cognitive constructs between the groups suggest that theoretically driven, generic population-based strategies operationalizing key socio-cognitive constructs for promoting physical activity may have utility for the general and diabetes specific populations. However, both diabetes groups reported significantly lower (p < 0.001) response efficacy (benefits of physical activity) scores, and higher scores for cons of performing physical activity than the non-diabetes group (p < 0.001). Further, the type 1 diabetes group had significantly higher (p < 0.05) physical activity cons scores than the other two study groups. The findings of this study may guide practitioners in designing population-based, physical activity programs that capitalize on generic strategies for the general and diabetes populations, and identify efforts as to where specific tailoring (e.g. emphasizing physical activity benefits) is needed for those living with diabetes.