A retired NYPD officer who rushed to the World Trade Center on 9/11 and was later diagnosed with a brain tumor was buried yesterday on Long Island.

More than 100 cops saluted as 41-year-old Officer Robert Grossman’s casket was carried from a Smithtown synagogue.

The Rocky Point resident was diagnosed with the brain tumor in 2006 and died Friday. He leaves a wife and six-year-old son.

His father urged that more medical treatment be provided for first responders.