Police were called to Monks Drive, Longridge, at 11:45pm on Wednesday evening (January 23) after a 53-year-old man was approached by three youths.
After asking the man for a cigarette, he was barged to the ground by the three individuals who went through his pockets.
They took a set of keys, a Samsung mobile phone, and cigarettes.
The man subsequently went to hospital with minor injuries.
A spokesman for Lancashire Police said: "Anyone that saw any suspicious behaviour can contact the police on 101 with log reference number 1623/23."