The boys, aged 15 and 16, have been released on conditional bail after they were arrested in connection with the robbery.
Police are appealing for witnesses after it was reported that two males approached a teenage girl as she walked along an alleyway off Remington Drive in Cannock.
The girl was grabbed from behind at around 8.50pm on Wednesday, threatened and showed a sharp object before her vape, wallet and mobile phone were stolen.
She was not hurt but was left shaken by the ordeal.
Officers arrested a 15-year-old and a 16-year-old boy, both from Walsall, on suspicion of robbery.
Both have since been released on conditional bail.
A spokesperson for Staffordshire Police, said: "Detectives are appealing for witnesses following a robbery in Cannock.
"At around 8.50pm on Wednesday it was reported that two males approached a teenage girl as she walked along an alleyway off Remington Drive.
"Enquiries are ongoing and any witnesses or anyone with information is asked to message Staffordshire Police on Facebook or Twitter or call 101 quoting incident number 807 of 8 June.
"Alternatively, contact Crimestoppers anonymously on 0800 555 111.
"Detectives are particularly keen to hear from anyone with relevant CCTV or dash-cam footage."