While the relevance of lead users has been well established for the early phases of the innovation process, such asideation and creativity, the relationship between lead userness and implementation and diffusion has not beeninvestigated. This is surprising, as the conjecture that lead user ideas are more likely to be implemented anddiffused than non-lead user ideas is a key tenet of lead user research. To test this conjecture we draw on a sampleof 87 internal process users in a large electronics firm who submitted ideas to an idea management system. 452ideas were suggested, of which 148 were implemented and 33 further diffused on the shopfloor. We find thathigher lead userness is positively and significantly associated with the likelihood of suggested ideas being implementedand diffused. This effect is substantial: Ideas coming from lead users were more than two times morelikely to be implemented and more than three times more likely to be diffused than ideas coming from non-leadusers. We conclude that lead user ideas are more likely than non-lead user ideas to be implemented and diffusedthroughout a social system, which arguably constitutes the ultimate success of any idea. Our research contributesto research on (internal) lead users, idea management systems, and idea implementation and diffusion.