John A. Paisley, a former high-level CIA employe whose body was found Sunday floating in the Chesapeake Bay, either killed himself or was the victim of an execution-type murder, Maryland police said yesterday.

Police said they could not determined how the death occurred from an examination of Paisley's decomposed body, discovered wearing two scuba diving belts weighing 38 pounds.

The death of the former CIA official, who once had access to highly sensitive military secrets, is being investigated as "suspicious," said William E. Clark, a Maryland State Police spokesman.

Maryland Chief Medical Examiner Dr. Russell Risher said Paisley, 55, who was last seen Sept. 24 sailing his 31-foot sloop on the bay, died of a gunshot wound above and behind the left ear.

The fatal bullet was fired from a 9 millimeter automatic pistol, the same type of gun Paisley was known to keep aboard his sailboat, Fisher said. The gun has not been found, Maryland State Police said yesterday, but one 9 millimeter cartridge was found on board.

"I see no reason to doubt that Paisley's gun fired the fatal bullet," Fisher said.

The medical examiner said the decomposed body, identified yesterday through dental records, made it impossible to check for traces of gun powder on Paisley's hands, evidence which Fisher said indicate suicide.

"There is no way of proving his death was a suicide," Fisher said. According to the pattern of the wound, the barrel of the gun that killed Paisely was pressed against his head when fired, he said.

Paisley, who was considered an expert sailor, once lived aboard his boat, the Brillig, for two years. He retired in 1974 as deputy director of the CIA's Office of Strategic Research. That office, according to a CIA spokesman, "produces analytic studies of foreign military programs and activities."

Paisley was in a position to know "highly sensitive" military secrets, according to a former CIA colleague.

The Brillig was found unoccupied but with its sails still set on the morning after Paisley disappeared. It had run aground near Point Lookout at the mouth of the Potomac River, 78 miles southeast of Washington.

Paisley's body was found Sunday afternoon about 15 miles north of Point Lookout near the mouth of the Patuxent River, according to the U.S. Coast Guard.

His body was dressed in blue jeans, a white pullover shirt and had no shoes, Fisher said.The diving weights were strapped around his waist. Paisley, according to his estrangled wife Maryann, had recently completed a scuba diving course.

According to a close family member who did not want to be identified, Paisley often had been depressed while at the CIA, but that in recent months he had been "happier and more talkative than he ever was before."

In December, Paisley, at the urging of his family, participated in an encounter group called Lifespring, the family member said. "It seemed to give him a new outlook on life," the relative said.

Paisley had worked for the past six months as a consultant for the accounting firm of Coopers and Lybrand. He recently separated from his wife, who lives in McLean, and moved into an apartment at 1500 Massachusetts Ave. N.W.

On the day he disappeared, Paisley was sailing west across the bay from Hooper Island to his home mooring at Solomons, Md. At 6 p.m., he radioed to a friend at SolomonS, retired Air Force colonel Norman Wilson, saying he was coming home after dark.

"He said he was going to do some paper work on the boat," Wilson said yesterday. "He sounded normal."