It occurred at the Esso service station on Harrogate Road, at approximately 6.20pm on Monday 26 September 2011, when two youths demanded money from the man behind the counter.
During the robbery the attendant was hit on the head with a piece of wood. He suffered minor injuries which were treated at the scene.
Shortly before the robbery a woman, who was leaving a shop on the same site, spoke with the two suspects.
A boy and girl, both local and aged 16, were arrested in connection with the incident a short time later. They currently remain in custody.
Detective Sergeant Chris Addison, of Harrogate CID, said:
I am appealing to the woman who spoke with the youths as she left the shop next to the service station to come forward as she is a vital witness.
I would also like to speak to anyone who has any information about the robbery and ask them to contact the police as soon as possible.
If you can assist with this investigation please contact DS Chris Addison, at Harrogate police station, on 0845 60 60 24 7 quoting reference number 12110163640. Or call Crimestoppers anonymously on 0800 555 111.