Jessy, your question is really kind of an awkward one to answer. CF being more common in children and teens than in adults? It's genetic, so really it's not a matter of it being more common to "get" in any one age group. It just happens that CFers usually don't live to a "normal" lifespan, so perhaps there are more kids and teens with it than adults. But this isn't because it's more "common" in kids or teens, it's just because many of us die before we get too too far into adulthood. And that's why you don't see as many adults with it.