PROVIDENCE, R.I. (AP) _ Gov. Bruce G. Sundlun's wife, Marjorie, was seriously injured in a traffic accident in upstate New York this morning, his spokewswoman said.

Mrs. Sundlun, 50, was hit by a car when she was walking with a friend in Geneva, N.Y., her hometown, press secretary Barbara Cottam said. Police said the accident happened at about 7 a.m.

She was transferred to Strong Memorial Hospital in Rochester, N.Y., where a spokeswoman said she was in guarded condition.

That means her injuries are extensive or her vital signs are not stable and could be life-threatening. The hospital spokswoman said Mrs. Sundlun suffered head injuries and broken bones.

Cottam said Sundlun cut short a scheduled daylong Cabinet meeting so he could be with his wife.

It appeared that Mrs. Sundlun was walking ahead of her friend and had turned to say something when she was hit by the car driven by a 76-year-old woman, Geneva Police Chief Frank Pane said.

''It looks like she just may have been in the wrong place at the wrong time,'' he said. Mrs. Sundlun was on the edge of the road at the time and the driver didn't see her, he said.

Police estimated the car was traveling 20 to 25 mph in a 30 mph zone.

Mrs. Sundlun and the governor, a first-term Democrat, were married in 1985. Both had previously been divorced and have grown children. Since the inauguration in January, Mrs. Sundlun has been her husband's special assistant, monitoring the state's social service agencies.