The serotonin-active meds lead the list. Talking to someone, getting at the root of the worry, making a plan to take care of it, these steps are essential. Medication can help sometimes, but it is not a cure. You would need a thorough eval to make sure it wasn't something else though. The key difference between ADD and ODD is volition.
Oppositional kids plan to defy, whereas ADD kids do it spontaneously, impulsively.
The treatment of ODD is mainly behavioral, although meds sometimes can help. Low doses of a beta-blocker like Corgard 20 mg can help with anxiety without causing depression. The other serotonin active anti-depressants, like Zoloft, as well as the MAO inhibitors are good for worry and anxiety. Plus Clonidine can help as can Wellbutrin in some cases. The main point to make is that meds are not a cure, but a potentially potent adjunct.