ditto

Use your Pokeradar in Route 218 (outside of Canalave City). The radar MUST be in effect in order to find one. And it's not likely that you'll find it with the first two or three uses, so be patient!
Good Luck!

First, you must receive the National Pokedex. To do so, you must see every Pokemon in Sinnoh, then you must show your Completed Sinnoh Pokedex to Professor Rowan, then you will receive your National Pokedex from Professor Oak.

Next, you will receive the Pokeradar from Professor Oak as a gift.

After you have done this, you can find Ditto by using the Pokeradar on Route 218; the patch of grass right outside Canalave City.

Hope this helps you!!!

First, get the Nat Dex, then you will recieve a Pokeradar from Oak. Use this at Route 218 and use it until you find a Ditto.

Hope this helps,
~Lukie.

Once you get the National Dex you can catch a ditto using your Poke Radar on Route 218.

Ok first off you MUST get the national pokedex (witch means you have to see all 150 Pokemon (if you need help finding 1 ask me I got them all) got it? Ok after fly over to Canalave City then run to route 218 go to the small patch of grass and use the Poke Radar in it (you get when you got national pokedex)then I'm sure go to the one with white sparkley lines just keep looking and looking until WALA ditto ! ! !

Kk hope I helped
Danik xx

You have to beat the Elite Four then talk to proffesor Oak after you complete the pokdex. He will give you the poke radar. You can then go to route 218 and in the patch of grass to the left near Canalave City and use the poke radar. It takes a while sometimes but eventualy find a Dito.
Hope I Helped