The so-called Good Samaritan car thief, who has been stopping female motorists in Baltimore to warn them of supposed car problems and then driving away in their cars, struck yesterday in the Washington area, Prince George's County police said.

The thief, described by police as a tall, clean-cut white man in his early twenties, stole two cars near Laurel in a manner almost identical to the way in which about two dozen cars have been stolen in the Baltimore area since late June, police said.

In the first incident, about 8:30 a.m., a man driving a 1983 Chevy Monte Carlo told a woman driving a 1986 Chrysler LeBaron on Muirkirk Road that one of her rear wheels was wobbling, police spokesman Cpl. Bruce Gentile said. Saying he was a mechanic, the man offered to test-drive the woman's car, Gentile said, and gave the woman his car keys to hold until he came back.

He did not come back, and the Monte Carlo that the car keys fit turned out to have been reported stolen the night before in Anne Arundel County, Gentile said.

About 10 minutes later, Gentile said, the man, driving the LeBaron, approached a woman in the Town Center Shopping Center in Laurel and told her something was dragging from the bottom of her 1985 Honda Civic. Again, the man gave the woman his car keys and offered to drive slowly away in front of her so she could see what was wrong. "He drove slowly away, all right, but he didn't stop," Gentile said.

The man stole an undetermined amount of cash from each of the women's purses, which they had left in their cars, Gentile said.