Some people have clubbed fingers that are really noticable....and it is true SOME people with a more advance stage of CF have bigger clubbed nails...although some with a mild form have bigger clubs...it gets confusing. It is a coralation between oxygen to the fingers...and they can become worse...like mine i have recently noticed my fingers have become more rounded, i have always had clubbed nails, but they seem to get more so rounded and my health has declined some but not alot. Clubbed nails, the not bad ones, look like you have good fake nails on -real round and pretty, some are so round looks like actual clubs on the end of the finger...its one of those things that isnt a definate thing..like if you have severe cf some dont have badly clubbed nails, and those with mild might have the more clubbed, vis versa....so no one can pin point really what causes it, they just know part of the reason is lack of O2 to the fingers and toes...its even been said the severity of the clubbing might be related to lack of O2 in the womb....anyway like i said they just know it has something to do with O2...its not anything life threatening (clubbed nails that is) so its nothing to worry about...they dont hurt, sometimes the nails are thicker so that may save a person hurt fingers...