In everyday life, one can link anticipated specific cues (e.g. visiting a restaurant) with desired actions (e.g., ordering a healthy meal). Alternatively, intentions such as "I intend to eat more healthily" present the option to act when one encounters the same cue. In the first case, a specific cue triggers a specific action; in the second, one must act in a more self-initiated manner. The authors compared such scenarios using functional magnetic resonance imaging. Participants were either instructed to respond in a particular manner to target events (cued condition) or told that they would score points for such responses, without being told that they were necessary (self-initiated condition). Although conditions differed only in the wording of instructions, the self-initiated condition was associated with poorer performance and greater activity in a predominantly frontoparietal network. Responses to targets in the self-initiated and cued conditions yielded greater activity in lateral and medial Brodmann area 10, respectively. The authors suggest that these results reflect differing demands for self-initiated versus externally cued behavior following different types of instruction, in line with the distinction between "goal intentions" and "implementation intentions" proposed by P. M. Gollwitzer and colleagues. (Contains 2 tables and 3 figures.)