A 16-year-old boy was punched twice in the face by robbers who stole his wallet.
The youngster was on his way home at 10.30pm when the assault took place.
Police described the attack on Lancaster Avenue, Accrington as random.
DC Helen Mercer of Accrington CID said: "Two lads approached the 16-year-old boy and one nudged into him. Then they came back and assaulted him. They punched him twice in the face and took his wallet which contained a driving licence.
"The area where it happened backs on to Gatty Park so we are appealing for anyone who may have seen anyone at this time on Tuesday, November 29."
The offenders are both described as white males, approximately 6ft tall, average builds and wearing dark clothing.
Anyone with information should contact police on 01254 353741.