I see what you mean, IMDB lists Forest Grove, Banks, and Hillsboro, Oregon as filming locations. The Empire Strikes Back really has only one location and that was in Finse, Norway. Everything else in the movie was filmed in the studio. I can't imagine why anyone would claim that there was any filming done in Oregon.
Bill
IMDb, as so often, has unconfirmed information about filming of Episode V in Oregon.
Dose anyone know anything more about this?
http://www.imdb.com/title/tt0080684/locations