Oh, geeze - the things you are doing are exactly right if he were about 10 or if he did not have ADHD. Unfortunately, almost all of those very standard and usually workable measures won't be effective. You really need a lot more information about ADHD. I super highly recommend that you buy the book, "The ADD/ ADHD Answer book," by Susan Ashley. Mainly because it saves me from typing about 20 pages of what to do. And then the same for a lot of years later.
In a nutshell, kids with ADHD lie because they have been doing things wrong for so long that they know stuff is gonna happen to them. Is sad to think that at this young an age they have figured this out - but its survival. They do things wrong because they have no filters. Meds do help. But they don't erase years of behavior. He will continue to make bad decisions unless someone is working with him to help him make good decisions. Every study I have seen says that behavior therpy should go hand in hand with meds. If all he is getting is meds - then what you are seeing is to be expected.
Unfortunately, talking to an 8 year old about making decisions hours or days later isn't really effective. You need to roll play those situations and do it time after time.
By the way, grounding him - at his age- is not effective. The punishment needs to be immediate, and then you move on. Kids with ADHD need structure, immediate reinforcement (both positive and negative), and consistency. Ashley has all of this in her book. It will reallllllly help. Please post if you have any more specific (or general) questions. Best wishes.
The interesting question is whether he would lie and steal if he did not have this ailment. Although this could be an innate character flaw, I should think it is problematical for your son to be shunted from one home to another. Two different environments, two sets of rules, two ways of dealing with him....
This is a problem that requires you and your ex-wife to work cooperatively to solve, preferably with the aid of a therapist.
My son is 9 and has adhd. He lies a lot and just this year started stealing things.he knows that it is wrong but he don't care. No punishment has ever worked for him.He has had it for about 5 years now. He is on meds for it along for all his learning and hearing problems. He is a kind and loving kid. So do not feel that u are alone in thinking it is just your kid.
Chances are he does care, but its really hard to show it after being disciplined countless times. You said he just this year started stealing. Any chance his meds need to be increased? Does the stealing tend to happen later in the day when the meds might be losing their effectiveness?
Sometimes kids with ADHD feel insecure and feel as if they have no control over their lives, so they steal to feel in control. You must also remember that they are impulsive as well and don't always think about what they are doing. When they do something wrong and get caught, they are scared and will lie, hoping nothing bad will happen. I know this because I have ADHD and have gone through the same thing.
Sorry to say that it is not common.Children only know what they see and hear. Teach your child that no one likes a thief and they do not owe anyone a lie. Let your child know that truth and trust are all they have in this world to build relationships with good people, and if they lie and steal most good people will not trust them or they will not want to be bothered with them.