I was playing Dealer's Choice - each player had 3 cards with 5 community cards. 3's were wild. I had 10, 5, 3 diamond, opponent had J, 4, 2 diamond. Community cards had A, K diamond. Since 3's were wild, I say I had highest flush, since I could make the 3 a Queen of diamonds. My opponent said that since my 3 was a diamond that he had high diamond in hand, the J, and that he wins. What is the ruling with wild cards in this situation?? Can I find this in writing somewhere??

From my wildcard games a wildcard is just that. It serves as the highest card in a flush or the needed card in a straight or as another card for a pair. In your hand you should have won the pot. I don't know where if anyplace this is written in stone but it is the way that it was always played in the games I frequented were wild cards were used.

yeah, you win the pot as not winning would make it a wild card game with restrictions. If you don't say any restrictions, there shouldn't be any so you should discuss this for future sessions but you should win. If there is a tie, I do know people to say that more natural hand wins, such as 4 Jacks using 2 wilds loses to 4 Jacks using 1 wild card. Most times its just a split pot but some games, a winner needs to be determined, like in pot games where the loser matches the pot and the winner takes the pot. If they split, there is no pot left to continue the action.