PM refers to the process associated with remembering to perform delayed intentions and increases in importance with advancing age. Naturalistic PM studies conducted in everyday life of healthy older adults are underrepresented and rare. To aim at this gap, the present dissertation focused on the question of what factors contribute to successful naturalistic time-based PM performance in real-life of healthy older adults. Three studies were conducted investigating the role of controlled cognitive resources and training (here: implementation intention and task-switching training) on PM in the second half of adulthood. With adherence rates far from perfect, the current work underlines the need of research on naturalistic time-based PM in real-life of older adults. Furthermore, two factors were identified that influenced naturalistic PM: controlled cognitive resources (here: task-switching and processing speed) and implementation intention strategy training. For the latter, however, effectiveness was only found for older adults with lower controlled cognitive resources.