Why do people sometimes struggle with decisions that once seemed relatively simple? This research suggests that comparing options leads people to lose sight of which decision attributes are important. Although the difference between important and unimportant attributes is often clear in the abstract, the act of making tradeoffs highlights what people must forgo on one attribute in exchange for a gain on another, which increases the perceived importance of trivial attributes in particular. This causes the variance in perceived importance across attributes to shrink, blurring the distinction between important and unimportant attributes. Four experiments demonstrate this phenomenon, explore the underlying mechanism, and show how it leads to increased choice difficulty and dissatisfaction with the choice experience.