This paper proposes a novel account of why intertemporal decisions tend to display impatience: People pay more attention to the opportunity costs of choosing larger, later rewards than to the opportunity costs of choosing smaller, sooner ones. Eight studies show that when the opportunity costs of choosing smaller, sooner rewards are subtly highlighted, people become more patient, whereas highlighting the opportunity costs of choosing larger, later rewards has no effect. This pattern is robust to variations in the choice task, to (...) the participant population, and is observed for both incentivized and hypothetical choices. We argue that people are naturally aware of the opportunity costs associated with delayed rewards, but pay less attention to those associated with taking smaller, sooner ones. We conclude by discussing implications for theory and policy. (shrink)