Dr. Kyra Mosel Hewitt, 45, a social psychologist who had worked for both government and private industry, died of cancer Wednesday at the Veterans Administration Hospital in Washington. She lived in Bethesda.

At the time of her death, she was director of a research project related to foster-care placements, which was jointly sponsored by the federal and Maryland state governments. It was associated with the Maryland Department of Human Resources.

From 1965 to 1976, Dr. Hewitt had been with IBM here. Before that, she had worked for the General Electric computer division. From 1957 through 1963, she was with the National Security Agency.

Dr. Hewitt was born in New York City. She came to the Washington area as a young girl and graduated from George Washington High School in Alexandria. She earned her undergraduate, master's and doctor's degrees from George Washington University.

She is survived by her husband, Kenneth Hewitt, and a foster son, Tony Harrison, both of Bethesda; her mother and stepfather, Jean and Harold Kilheffer of Arlington; her father, James N. Mosel of Washington, and two sisters, Elained Metallo of Denver and Milita Liebowitz of New York.

The family requests that expressions of sympathy be in the form of contributions to the American Cancer Society.