If you were under 18 at the time, the first question I have is whether your case was in juvenile court or adult court. If it was in juvenile court, then that record may be sealed. However, if the second DUI was within 10 years of the first, then the first will count as a prior and the second DUI will be prosecuted as such. If your case was in adult court, there is not a realistic way for it to be totally removed from your record, as CA does not offer true expungement. If you have an attorney, I strongly suggest that you talk to him or her about it, as they will be in a much better position to advise you than any of us on here. Good luck.
Since your question is a little confusing I will just say the following...
A DUI conviction as a minor under the age of 18 years old cannot be charged or even considered as a prior alcohol offense in any criminal court... But the DMV is allowed to consider any juvenile suspension based on an alcohol offense when setting the terms of suspension based on the new offense. Depending on your age your attorney will advise you about your license suspension options if any.