PHOENIX, Ariz. (AP) _ Ruth E. Carson, mother of ''Tonight'' show host Johnny Carson, has died at her home in the suburb of Paradise Valley at the age of 84.

A friend, Darrell Dudley of Sun City and Norfolk, Neb., said Mrs. Carson had been ill for the past four years and had ''nurses around the clock'' the past couple years. She died Friday

Mrs. Carson and her late husband, Homer ''Kit'' Carson, had been winter visitors to Arizona for seven years before moving here in 1978. Her husband died in 1983 at the age of 83.

Dudley's wife Joanna and another friend, Jerry Huse, publisher of the Norfolk (Neb.) Daily News, said they believed Johnny Carson inherited his sense of humor from his mother.

''Ruth had a great sense of humor and was really a sharp lady,'' said Huse. ''The genes must have flowed from her side.''

''She really had a fine mind and a sense of humor,'' said Mrs. Dudley. ''Johnny was more like his mother.''

In addition to Johnny Carson, Mrs. Carson is survived by another son, Richard, and a daughter, Catherine Sotzing.

Funeral arrangements were private.