This study examined the relative benefits of physical and cognitive activities on simple and complex cognitive task performance in older adults. Participants were 24 young (18-27 years), 24 young-old (65-74 years), 24 middle-old (75-84 years), and 24 old-old (85-92 years) adults. Participants recorded the amount of time engaged in physically and cognitively stimulating activities as well as the effort exerted during these activities. They also completed a simple and complex version of a visual imagery task. Age-related declines were evident in activity and imagery performance. Both physical and cognitive activities were related to better cognitive performance. Furthermore, cognitive activity was a stronger predictor than physical activity of the complex, but not the simple task. However, within each activity domain there were no significant differences between performance on the simple and complex task. These results suggest that physical and cognitive stimulation are useful in protecting against cognitive decline with age, but that they may exert their influence via different paths.