Young people hoping to get a job were instead victims of an identity theft which saw dud cheques issued in their names.
Police said it was one of the new scams to have emerged last year - including one where conmen offered a free app to prevent theft but stole the phones instead.
Nine people aged 18 to 25 who responded to job offers on an internet forum were invited to group interviews in a public place, such as a café or park.
They were asked to provide signatures, bank account information and their identity cards for employment purposes, according to Ip Wai-kin, chief inspector of the police's commercial crime bureau.
Their would-be employers asked the interviewees to wait while they photocopied the ID cards and other information. But they never returned. The conmen then used the stolen identities to open chequebook accounts.
They went on to cheat another eight people who accepted the cheques in payment for goods advertised on the internet - only to find the bank accounts were empty.
Three of the swindlers were caught after trying to take money from interviewees' bank accounts and were jailed for theft and deceit.
Police said the use of the internet to target victims was on the rise. In 2011, 11 out of 43 employment scams involved the internet, with 14 victims. Last year, there were 39 victims in 13 out of a total of 21 scams involving jobseekers.
Ip said most of the scams started on discussion forums and warned: "Jobseekers should be more vigilant if they are asked to participate in interviews in public places."
His colleague Brian Pau Siu-ming said the smartphone anti-theft app scam had netted one victim who was just 13 years old.
Another member of the crime bureau team, Siu Wai-sing, said 87 people were conned into investing a total of more than HK$13 million in two non-existent mainland companies.
They were presented with an opportunity to invest in exciting new start-ups and even taken on field trips designed to convince them of the profits to be made.