A man indecently exposed himself to two 14-year-old girls as they walked along a footpath in Kirk Hallam early on Sunday evening.
A spokesman for Derbyshire Police said: “The girls were walking along the Nutbrook Trail off Ladywood Road, when they noticed a man come out from the bushes.
“They continued to walk along the trail and as they turned around they noticed that the man had indecently exposed himself.”
The offender has been described by the teenage victims as white, aged in his early 20s, around 5ft 7ins tall.
He was wearing a dark hooded jumper and blue jeans.
The incident happened at around 6.30pm on Sunday, September 28.
Anyone with information about the incident or who saw a man fitting that description in the area is asked to call Derbyshire police on 101 quoting crime reference 41065/14.
You can also report a crime anonymously by calling Crimestoppers on 0800 555 111.