past tense

Is it 「かっこいかった」or「かっこよかった」?

I've heard both, but which is it? Or do they mean the same thing?

Thanks!

かっこよかった is the right word.

かっこいい is the "present" tense i-adjective, but when it changes forms to negative or past, etc., the いい part goes back to the original word よい. So...

"is not good looking" かっこよくない
"was good looking" かっこよかった
"was not good looking" かっこよくなかった

Some people might say "kakkoikatta" just to be playful, though. The right form is "kakkoyokatta."

Thanks AK, I get it now (^-^)