Arthur Sylvester, 78, a newspaperman who served as chief spokesman for the Defense Department from 1961 to 1967, died of cancer Friday in Cold Spring, N.Y.

He was Washington bureau chief of The Newark (N.J.) News when he was named assistant secretary of defense for public affairs. As such he was the Pentagon's spokesman for Secretary of Defense Robert S. McNamara.

Mr. Sylvester's tenure proved comtroversial, particularly following the Cuban missile crisis in 1962, when President John F. Kennedy ordered a naval blockade of Cuba.

Kennedy was accused later of manipulating the news and of lying about the government's knowledge of Russian missiles in Cuba two days before it was to confront Russia with the evidence.

Mr. Sylvester at that time contended that "the government has the right to lie." He justified this later in testimony before a congressional hearing:

"Obviously, no government information program can be based on lies; it must always be based on truthful facts. But when any nation is faced with nuclear disaster, you do not tell all the facts to the enemy."

There were other information restrictions that Mr. Sylvester implemented at the direction of McNamara and that also caused controversy. They included requiring Pentagon monitors to accompany newsmen when they interviewed Defense officials.

Despite the controversies which arose also over Vietman and other Defense Department issues, Mr. Sylvester retained the respect of many of his newspaper colleagues. His resignation was accepted with "deep regret" by President Lyndon B. Johnson. Mr. Sylvester received the Distinguished Public Service Medal.

He was born in Montclair, N.J., graduated from Princeton University and then worked as a shipping clerk and salesman for the Macmillan Co. publishing house in New York.

He joined The Newark News in 1924 as a reporter and later was city editor for eight years before coming to the Washington bureau of the newspaper in 1944.

In 1977, he was elected to a two-year term as mayor of Cold Spring.

He is survived by his wife, the former kathryn Ferguson, of Cold Spring; a son, Anthony I., of Mifflinburg, Pa.; a daughter, Natasha Scarola, of New York City, and five grandchildren.