Mnemonic strategies generally improve prospective memory (PM) performance. However, little is known about why people use such strategies. In the Motivational-Cognitive Prospective Memory model, task importance is thought to influence performance via multiple mechanisms, including increased strategy use. Our main purpose was to test this mechanism: higher PM task importance was hypothesized to cause greater strategy use. We also tested whether importance would specifically increase the use of more effective (external) strategies. Participants reported their strategy use for two hypothetical PM tasks. As predicted, they listed more strategies for more important tasks. This result demonstrates one mechanism for motivational effects in early phases of the task. We found weaker support for the prediction that participants would selectively increase their use of better strategies for more important tasks. This finding supports a relatively pessimistic view of meta-memory in PM, at least when it comes to modulating one's use of dependable strategies. Copyright © 2013 John Wiley & Sons, Ltd.