Sleep for children is so important and it is just a matter of going to sleep the same time every night. A lack of sleep could be the cause of your childresn ADHD as well or at least contributing to it. On the other hand that could be the reason that your child can not or has diffuculty going to sleep…it is a viscious circle sometimes. Bottom line…you need at least 8-10 hours every single night preferrably at the same time.