Although the policy diffusion literature comprises a large number of methodologically sophisticated papers, very little is known about basic issues such as how often states actually look at others’ policies, whose policies they look at, and when they look. We study policy research briefs prepared for legislators to focus on policy knowledge diffusion. We find that policy researchers frequently reported on others’ policies. We also find that factors such as innovativeness and proximity affect how often a state’s policies are studied. More generally, we find evidence of fairly sophisticated learning as policy makers looked at others’ policies in nuanced and varied ways. Our findings suggests that information about policies diffuses through systematic and targeted research during the policy-making process. This policy research disproportionately focuses on neighbors and states likely to have good policies, but it also uncovers ideas from less obvious states.