Gladys Nelson Smith, 90, portrait, landscape and still-life painter here for more than 50 years, died Monday at the Kensington Gardens Nursing Home. She had Parkinson's disease.

She had been a resident of Chevy Chase from 1949 unitl last June. She was the widow of Errett Garrison Smith, an attorney, who died in 1974.

Mrs. Smith, who worked in ouls, watercolors and pastels, had her first one-person show in 1979 at the Veerhoff Galleries here. Earlier, her paintings had been included in exhibits at the Corcoran Gallery.

She had won honors from the Corcoran School of Art, which she had attended after coming to the Washington area in 1924, and from the Washington Society of Artists. She also had exhibited this summer at the Catepet Gallery in Frederick, Md.She and her husband had owned a small farm near Frederick for many years and she had painted numerous landscapes there.

Mrs. Smith was born in El Dorado, Kan. She graduated from the School of Fine Arts of the University of Kansas in 1918. She started her career as an artist in Minneapolis, Kan. Later, she worked at the Chicago Art Institute.

Survivors include two sisters, Josephine Nelson of Chevy Chase, and Loraine Nelson Shulze of Cary, N.C.