MWM is right... ADHD is rarely a stand-alone diagnosis (not "never"... I have one kid that IS just ADHD minus the Hyper).
If ADHD is an early diagnosis, it will usually end up one of two ways... or both, if it takes too long to get the second type!
1) ADHD plus... can include other developmental issues such as Developmental Coordination Disorder (DCD), Auditory Processing Disorders (APD), sensory processing disorder (SPD)/Sensory Integration Disorder (SID), as well as learning disabilities and other challenges. Many of these "add ons" can be missed or dismissed as not important. They DO matter.
2) Instead of ADHD... In reality, ADHD is just one of a whole spectrum of challenges, of which two common pervasive dxes that can come instead are Autism Spectrum Disorders (ASD) or Aspie. Many of the "plus" items are an integral part of Autism Spectrum Disorders (ASD) dxes - there just needs to be enough separate pieces, including specific social skills issues, for an Auditory Processing Disorders (APD) diagnosis. Some kids are "almost" but not quite officially on the spectrum, others definitely are. There are MI challenges that can look like ADHD as well.
One way or the other... it pays to get more answers. Even if you still don't get ALL the answers, each additional piece to the puzzle is a huge win.