multiple where statements in big select

If I deal only with one parameter in my where

WHERE (   (ADB.param1 = COALESCE(@param1, ADB.param1))

then when I send param1 I get only one row and all rows if param1 is null

but when I add second parameter check

    WHERE (   (ADB.param1 = COALESCE(@param1, ADB.param1)) 
AND (BDB.param2 = COALESCE(@param2 , BDB.param2))  )

I get nothing when sending only param1. But I still must get 1 row. But get nothing :(