A man who vandalised Facebook tribute sites for two dead children has been jailed.

Self-confessed "troll" Bradley Paul Hampson, 29, of Tarragindi in Brisbane's south, posted pictures of penises and wrote offensive messages on the two sites in February last year.

On one Facebook tribute site for the 12-year-old boy, he wrote "woot I'm dead" across an image of the dead child.

He also morphed a photo of the boy's face inside a woodchipper and made it appear blood was coming from the machine.

On another, he wrote sexually explicit comments implying he was responsible for raping and killing the eight-year-old girl.

"My definition of pleasure ... listening to her ribs crack," he wrote. "I got mad ... so I murdered her."

To post his comments, Hampson used the name of a Bundaberg man who he claimed to have gone to school with.

Hampson said the man whose identity he used had been bullied by other students at his school.

The court was told that man told police he was distressed his name had been used to make such comments.

The court also heard when detectives examined Hampson's personal computer, they found almost 200 images that depicted children as the victims of abuse and sadism.

They also found images of missing UK girl Madeleine McCann and murdered UK boy James Bulger with penises superimposed on their faces.

Hampson today pleaded guilty to distributing child exploitation material, using the internet to menace, harass or cause offence and possessing child exploitation material.

Judge Kerry O'Brien sentenced him to three years' jail and ordered he be released after he serves 12 months.

Taking into account seven-and-a-half months Hampson has already served behind bars, he will be out of prison in September.