The would-be policeman waved down the woman, who is in her twenties, on a road in Nacka. He asked for the woman’s driving licence, which he then took to his own car, before returning it to the woman.
She became suspicious and called the real police when he refused to show her his police identification.
Police in Nacka say that the man was not a real police officer, and has been reported to have stopped cars elsewhere in the capital.
“Maybe it was someone who dreamed of becoming a policeman, but never did, and wanted to know what it felt like to stop someone,” said Nacka police commander Christer Angeria.
Police say they have the man’s car registration number, and hope to be able to track him down. The crime of impersonating a public official can lead to a six month prison sentence.