He can be quite pompous and vain, certainly when it comes to his own abilities as a detective.
Is prone to unpredictable changes in mood. Holmes is possibly a sufferer of bi polar, although I don't know if he was ever diagnosed. During these black moods, Holmes tends to brood alone in his rooms at Baker Street.
On the whole, he is emotionally detached and doesn't make a habit of consoling victims of crime or their recently deceased.