A 17-year-old Canberra boy who pleaded guilty to blackmailing men using the gay dating app Grindr, including one who went on to take his own life, has been sentenced to six months in detention.

The Canberra teenager pleaded guilty to blackmailing two men, as well as growing cannabis in his bedroom, in the ACT Childrens Court earlier this week.

The boy and three others, including his older brother, were charged after they demanded money from men they had lured using the app, and then threatening to accuse them of being child molesters.

One of the youths told an alleged victim the group were "pedo hunters", according to police.

Sophisticated scam

Chief Magistrate Lorraine Walker today described the boy's crime as callous.

The first blackmail charge against the boy was related to a man he and his brother arranged to meet through Grindr.

"They sought money and threatened to ruin his life," Chief Magistrate Walker said.

The second charge was related to the blackmail of a man who went on to commit suicide.

The boy threatened the victim with a dossier he had made which detailed social media exchanges, images and excerpts of ACT laws.

The group met the man at the Mawson shops where they threatened to release the material unless he handed over money and his phone.

They later went to the man's house where one of the group threatened to call the police.

The 17-year-old then continued to issue threats to the man on Facebook, but those were posted after the man had taken his own life.

Chief Magistrate Walker said she could not make a formal finding that the boy's offending directly contributed to the man's death.

"There's a close correlation between (his) offending and (the man's) death," she said.

Immature view of homosexuality

Police described the 17-year-old as the leader of the group after finding dossiers he compiled on the victims, recording who was targeted and how much they had paid.

The court heard he appeared to have several motives from financial gain, retribution over his father's abuse as a child and a hatred of gay men who he said were all paedophiles.

Chief Magistrate Walker said "(the boy) seems to have an immature view that has conflated homosexuality and paedophilia".

"It goes without saying that these are as different as chalk and cheese," she said.

She also expressed concern about a pre-sentence report suggesting he did not think differently, even now.

Ms Walker told the court she did not believe rehabilitation could be achieved through supervision.

The boy was formally sentenced to 19 months, but with time already served and a suspended sentence he will only spend another three months behind bars.

Three others charged over the scam are still before the court.