He leaked one of Miss Johannson, 26, posing in the nude to a celebrity website and others of Black Swan star Miss Kunis.
However, in his first TV interview after appearing in court Chaney denied he had ever tried to blackmail the stars. Police believe there were as many as 50 victims.
Chaney, from Jacksonville, Florida, said his fascination with Hollywood stars became overwhelming and he didn't know how to stop his addiction.
Apologising to his victims in an interview with his local TV station, he said he was relieved when he was arrested under the FBI's so-called 'Operation Hackerazzi'.
"I know what I did was probably the worst invasion of privacy someone could
experience," he said.
"I'm not trying to escape what I did. It was wrong. And I have to just face that and go forward."
Chaney said he was able to use his computer skills to hijack the emails of the celebrities. Every time they received an email he would receive a copy.
FBI officials said he was able to work out passwords by reading information about the stars.
"It started as curiosity and it turned to just being addictive," said Chaney. "It is the people you see on the big screen as heroes and you wonder about. I took that wonder too far. I was pretty stupid."
Asked what he did with the emails, Chaney added: "Nothing. It was almost like a completely uncensored blog. I wasn't saving the emails to blackmail someone."
Chaney said he plans to plead guilty to multiple charges of identity theft, unauthorised access to a protected computer and wiretapping. He said he did not sell the photos of Miss Johansson, but Steven Martinez, assistant director in charge of the FBI's Los Angeles office, said he passed on the photos to a website.
"Celebrity information is highly marketable," said Mr Martinez.
After appearing in court in LA on 26 charges Chaney was freed on bail.
His mother said her son "had too much time on his hands", adding: "He's a good kid, he just made a big mistake."
