Raikkonen, who was a world champion with Ferrari back in 2007, left F1 two years ago and dabbled in both NASCAR and World Rally Championship, before it was announced earlier this week that he has signed for Lotus Renault on a two-year deal.
And the Finn admits participating in other forms of motor racing ultimately helped him decide he wanted to return to F1 - a sport he claims he was always passionate about.
"The main reason [for returning] was that I never really lost the passion for racing in Formula One, just maybe for all the other things around it," Raikkonen told the official F1 website.
"But when I did some NASCAR races this year I noticed I was increasingly missing the racing side - to race against each other - because in rallying you really race against the clock.
"And then I got the call from certain people in Formula One. All sorts of things happened and we managed to have a nice conversation with Lotus Renault GP and make a deal - I'm really very happy with that."
Raikkonen revealed there was also interest from Williams, and admitted he has not caught much of the last two seasons, which saw Red Bull's Sebastian Vettel crowned world champion on both occasions.
"Really there were two options - it was this team or Williams. And everything worked out with Lotus Renault GP as we wanted, so that's really the reason.
"I didn't follow Formula One much at all last year. This year I followed it a bit more but not really any specific team.
"I watched the last 20 laps of the last race, the Brazilian Grand Prix, and because I knew this was going to happen I also watched how the Lotus Renault GP team did.
"But before that I didn't know anything about what was going to happen or that there would be a deal in Formula One for next year, so I just watched Formula One as a whole.
"I saw a few races but nothing special."
In the two years that Raikkonen has been absent, there have been plenty of rule changes in Formula One, of which the Finn is particularly concerned about the Pirelli tyres.
"Comparing 2009 to next year the biggest difference will probably be the tyres.
"I don't think there is a lot of difference with the cars. DRS [Drag Reduction System] is a new thing but this is basically similar to before. The button that used to be for the front wing has disappeared, so now it's for the rear wing.
"I would guess the main difference is really the tyres."
Now 32, Raikkonen does not believe he has changed much as a driver since he last took to the wheel of an F1 car, and doubts it will take him long to get back to the groove of things.
"I'm interested to get back into the car, I'm two years older now and I don't think anything else has really changed.
"I'm really looking forward to coming back. At least Formula One is something where I know how everything works as I've been there for many years - compared to rallying when I didn't know what would really happen. Then I went to NASCAR and I had no clue how it would be.
"So in that way it should be much, much easier to come back and it should be pretty normal."
Raikkonen's return means there will be six world champions lining up on the grid for the 2012 season, including Vettel, Jenson Button, Lewis Hamilton, Fernando Alonso and Michael Schumacher.