Mourinho said he was in complete control of all playing matters between 2004-07 and also gave an insight into the behind-the-scenes activity that led to the signing of AC Milan striker Shevchenko for 30 million pounds.
"The owner never, never during my time did he try to interfere in the basic things of the manager," the 50-year-old Portuguese told reporters.
"The basic things are training sessions, team selection, profile of the players you want to bring."
Mourinho, who signed a four-year contract earlier this month to return to Chelsea, said the Shevchenko transfer was a good example of how he and the billionaire owner used to work in tandem in his previous three-and-a-half-year stint at Stamford Bridge.
"We wanted to buy Samuel Eto'o from Barcelona," said the former Real Madrid, Inter Milan and Porto manager. "Why? Because he was the only player I could play with Didier Drogba, changing the system to two strikers.
"The boss [Abramovich] did everything to bring Eto'o. In the end Barcelona said 'we don't sell, forget it'.
"After that we went to other options and got to Shevchenko, and I was happy with Shevchenko," Mourinho said.
"When you buy 20 kids, not 20 kids will go to the first team, and even with the top dogs when you pay 30, 40, 50 or 60 million sometimes it just doesn't work and it doesn't mean you or the club made a mistake."
Ukrainian international Shevchenko was one of the finest strikers in world football but he flopped at Chelsea and was never able to recapture the form that won him the 2004 European Footballer of the Year award.
Looking forward, Mourinho said he was happy to work with sporting director Michael Emenalo over incoming transfers.
"There are many things in a manager's job you cannot do, or if you do, you don't do it properly," Mourinho said. "Or if you do, it means you are losing your influence in other areas that become more and more important.
"So it's important you have around you some structures that can deliver the best possible information. The scouting area is a very difficult area for a person like me.
"I cannot travel because I have more important things to do inside the club. I also cannot travel because everybody knows I'm travelling, everybody knows who I am, everybody knows the player I'm looking for.
"Michael is working well. The club are doing good work there and Michael and his staff will provide me with the kind of information I need."
Mourinho also scotched the idea Europa League winners Chelsea were his second-choice club behind Premier League champions Manchester United, who decided to appoint Everton manager David Moyes last month when Sir Alex Ferguson announced he was retiring.
"I would turn down everyone in the world for Chelsea," he said, before adding that he was aware a long time ago that Ferguson was planning to quit.
"I knew Ferguson was retiring many months ago... and I'm so happy with this trust because it's big news
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