The Columbian reports that the sheriff's office says the skull found Saturday may be that of 29-year-old Sam Stefonek, 29, who was reported missing in an area northeast of Kelso in August 2010.
He reportedly had argued with a girlfriend before disappearing.
His phone and a few other items of clothing were found previously.
Sheriff's Chief Criminal Deputy Charlie Rosenzweig says the skull did not show any signs of trauma. It was found in deep woods about a mile from where Stefonek was last seen.
The county medical examiner will try to make a positive identification.