In recent years, research on rewards has been conducted very actively. Existing studies have primarily focused on the content of rewards (e.g., type, size). Generally, the size of a reward is closely related to the probability of the reward being realized. In particular, the size and probability of rewards are often in a trade-off relationship: when rewards are large, the probability of receiving them tends to be low, and when the probability is high, the rewards tend to be small. Nevertheless, research considering this trade-off relationship of rewards has been very limited. Accordingly, this study focused on the size and probability of rewards. Specifically, we sought to identify, using regulatory motivation, under what conditions consumers place greater weight on size over probability and under what conditions they place greater weight on probability over size. The results of Experiments 1 and 2 showed that consumers with promotion motivation evaluated rewards with large content but low probability more positively than rewards with small content but high probability. However, consumers with prevention motivation evaluated rewards with small content but high probability more positively than rewards with large content but low probability. That is, a regulatory fit effect emerged in the evaluation of reward programs. Meanwhile, Experiment 3 of this study went beyond existing research on regulatory fit to examine the moderating effect of regulatory fit. Specifically, we distinguished between situations where regulatory fit can influence the evaluation of reward programs (e.g., when past experience with reward programs is positive) and situations where it cannot (e.g., when past experience with reward programs is negative) to identify the moderating effect of regulatory fit. The results showed that when past experience with reward programs was positive, a fit effect between reward type and regulatory motivation appeared. However, for negative experiences, the fit effect appeared only for consumers with promotion motivation and did not appear for consumers with prevention motivation. That is, consumers with promotion motivation evaluated rewards with small content but high probability more positively than rewards with large content but low probability. In contrast, consumers with prevention motivation showed no significant difference between rewards with small content and high probability and rewards with large content and low probability.