Most American colorectal cancer deaths can be prevented with colonoscopies. Colorectal cancer (CRC) killed 28,000 men and 25,000 women in 2017. Men undergo fewer colonoscopies than women, but it is ex ante unclear whether women or men take the risk of CRC more seriously. On one hand, women are expected to live longer, increasing their benefit from a colonoscopy, and on the other hand, women are at lower risk of CRC, decreasing their benefit from a colonoscopy. I estimate a dynamic discrete-choice life-cycle model that controls for gender-based differences in lifespan and how CRC develops. The model also factors in how screening and CRC history affect the probability of developing CRC. I find that women act as if they take the risk of colorectal cancer more seriously than men and that if men had the disutility parameters women act as if they have, it would save an additional 174,000 life-years for American men who are currently at age 50, a 39% improvement. This is larger than the gains from all men getting screened at the rate of college-educated men who live with another adult (89,000 life-years, a 20% improvement) or the gains from making colonoscopies mandatory for men at age 60 (111,000 life-years, a 25% improvement). I conclude by discussing the impact of offering monetary incentives and propose policies informed by behavioral economics to increase the rate of colorectal cancer screening.