Many ADHDers, children and adults alike, struggle with organization. A term that is used a lot now is "executive functioning." That means the skills to get things organized, prioritize what needs to be done first, and generally sort things out. I call it the "Mom" part of the brain, as in "do this now," "do that first," "why are you taking so long to do that?" It has nothing to do with how smart you are. You could be a super genius, but without the "mom" part working, you will never be able to show anybody the paper on which you solved global warming--because you can't find the paper. Getting help from a coach is one strategy to help with organization (a large garbage bin prominently placed is another). You can't "all of a sudden" become organized. Pick one or two areas that you really care about. Make it a "game" to improve your organization. Forgive yourself when you lose the game sometimes.
Although, I must say, as a Mom, I rarely feel organized :). More and more, I count a day a success when I have managed to keep my head above water and not forget to pick my children up from somewhere.